Ink set, recording method, recording device, recording system, and recorded object

ABSTRACT

It is an object of the present invention to provide an ink set which makes it possible to obtain recorded images that have a broad color reproduction range and a high saturation, as well as glossiness without conspicuous graininess caused by dot expression, and which in particular makes it possible to achieve an extreme suppression of graininess caused by dot expression in cases where the ink set is used on media that have a coating layer, and to obtain recorded images with extremely superior coloring characteristics in cases where the ink set is used on ordinary paper. The present invention provides an ink set comprising at least a yellow ink (Y), magenta ink (M), cyan ink (C) and red ink (R), wherein the L* values in the CIE-stipulated Lab display system of aqueous solutions of the respective inks diluted 1000 times by weight are in the following ranges: (Y): at least 89 but no more than 94, (M): at least 76 but no more than 93, (C): at least 74 and no more than 87, (R): at least 55 and no more than 74.

CROSS-REFERENCES

The present invention relates to an ink set, recording method, recordingapparatus, recording system and recorded matter which realize a superiorcolor reproducibility and reduction in metamerism, and more particularlyrelates to an ink set which is superior in terms of the colorreproducibility of recorded images, and which can reduce metamerismwithout any conspicuous graininess caused by dot expression, even ifspecial inks other than yellow, magenta and cyan (YMC inks), such as redinks, violet inks or the like are not used, an ink set which is capableof high-quality output in both monochromatic and color images, which issuperior in terms of the color reproducibility of recorded images, whichcan reduce metamerism without conspicuous graininess caused by dotexpression, and which makes it possible to obtain a stable gray balance,and an ink set, recording method, recording apparatus, recording systemand recorded matter which make it possible to alleviate metamerism bymeans of a simple construction without greatly reducing the region ofcolor reproduction.

BACKGROUND

Ink jet recording methods are printing methods in which recording isperformed by causing the jetting of small droplets of ink (inkcomposition), and causing these droplets to adhere to a recording mediumsuch as paper or the like. Such methods are advantageous in that clearimages with a high resolution can be printed at a high speed using arelatively simple apparatus. Ink sets used in such ink jet recordingmethods include ink sets comprising respective cyan (C), magenta (M) andyellow (Y) inks, ink sets in which a black (K) ink is added to theseinks, and the like. For example, an ink set combining cyan, magenta andyellow inks which makes it possible to obtain good images, especiallyimages with a good hue, in addition to possessing light resistance andwater resistance, has been disclosed (Japanese Patent ApplicationLaid-Open No. 10-120956).

In recent years, ink sets having light and dark inks which differ fromeach other in color density while being of the same color have beendeveloped in order to realize both a broader range of colorreproducibility and a suppression of conspicuous graininess when imagesare expressed by dots (a state in which the dots appear to be grainywhen observed with the naked eye). For example, there are ink sets whichhave the four inks of C, M, Y and K as dark inks, and the four inks oflight cyan (Lc), light magenta (Lm), light yellow (Ly) and light black(Lk) as light inks.

By performing recording while varying the amount of coloring materialapplied per unit area of the recording medium (i. e., varying the duty)using such an ink set comprising light and dark inks, it is possible toreduce the grainy sensation caused by the ink dots, and to obtain anoutput of color images with a high image quality comparable to that ofsilver salt photographs.

However, images in recorded matter formed using such conventionalpigment ink sets suffer from the following problem: namely, a phenomenonin which the hue of the recorded images varies when the light sourceproviding illumination varies, i. e., metamerism (light sourcedependence), occurs. For example, ink sets comprising a yellow inkcontaining C. I. pigment yellow 110, and ink sets for ink jet recordingwhich provide clear, high-quality images and superior light resistanceon special coated media, have been developed as techniques for reducingthis metamerism. However, in cases where images are formed using suchink sets, the green color reproducibility is inadequate (Japanese PatentApplication Laid-Open No. 2002-332440, Japanese Patent ApplicationLaid-Open No. 11-228888).

Furthermore, ink sets comprising special color inks such as green inks,red inks, violet inks or the like besides yellow, magenta and cyan inksfor the purpose of suppressing graininess caused by dot expression,improving the range of color reproducibility and reducing metamerism,have also been reported. For example, an ink set comprising a violet inkand red ink has been disclosed (Japanese Patent Application Laid-OpenNo. 2001-354886).

Such special color inks have a low lightness; however, in the case of ahigh resolution of 720×720 dpi or greater, since the radius of the dotsapplied to the media is small, graininess caused by dot expression ispermissible even in cases where special color inks with a low lightnessare deliberately printed in high lightness areas. However, at a lowresolution such as 720×360 dpi, since the radius of the dots applied tothe media is large, the graininess caused by dot expression becomesconspicuous in cases where special color inks with a low lightness aredeliberately printed in high lightness areas, so that such printingcannot be allowed. Accordingly, it is difficult to achieve both areduction in metamerism and a suppression of graininess in highlightness areas using ink sets comprising special color inks with a lowlightness. In this case, it might be thought that both a reduction inmetamerism and suppression of graininess in high lightness areas couldbe achieved by converting special color inks into high lightness inks;in such cases, however, the reproducibility of high-saturationlow-lightness colors drops.

Furthermore, an increase in the image quality and stability of the graybalance are required in the printing of monochromatic images. Arecording apparatus using two or three types of black inks withdifferent pigment concentrations (Japanese Patent Application Laid-OpenNo. 11-48502), a recording apparatus which separately performsmonochromatic output and color output with at least one type of colorink and concentration types greater than the number of colors (JapanesePatent Application Laid-Open No. 11-320924) and the like have also beenproposed in order to increase the reproducibility of monochromaticimages; however, these apparatuses cannot output both color images andmonochromatic images in a favorable manner. Moreover, since ink jetprinters use liquid inks, effects of changes in the external environmentthat cause the viscosity of the inks to vary may cause minute colorvariations. Accordingly, stability of the gray balance is required.

Conventionally, furthermore, ink sets of this type have included inksfor alleviating metamerism that have colors equivalent to specifiedtertiary colors obtained by the mixing of the three types of primarycolor inks cyan, magenta and yellow (CMY), and that have a spectroscopicreflectance that is flatter than the spectroscopic reflectance of anyspecified tertiary color. Furthermore, at least one color in the colorimages is reproduced using a metamerism alleviating ink and at least oneof the three types of primary color inks CMY; as a result, the colorlessspectroscopic reflectance characteristics that are reproduced are madeflatter than in the case of reproduction by the mixing of the threetypes of primary color inks CMY (for example, see Japanese PatentApplication Laid-Open No. 2002-225317).

Since metamerism alleviating inks must be prepared in the conventionalink sets described above, the following problems are encountered:namely, the structure of the ink set is increased in size, and inkcontrol also becomes more complicated. Furthermore, there is also amethod in which metamerism is reduced by altering the Y ink in thecombination of the CMY ink set; in this case, however, the followingproblem arises: namely, the color reproducibility in the green directionin high-lightness regions is greatly reduced.

Accordingly, it is an object of the present invention to provide an inkset which realizes superior color reproducibility and a reduction inmetamerism.

Furthermore, it is another object of the present invention to provide anink set, recording method and recording system that make it possible toobtain recorded images which are superior in terms of colorreproducibility, and in which metamerism is reduced without anyconspicuous graininess caused by dot expression, without using specialcolor inks other than YMC inks, and in particular, an ink set whichmakes it possible to obtain recorded images that show no color variationcaused by the application of pressure in addition to having theabovementioned superior performance values, and an ink set which ishighly reliable as an ink set for use in ink jet recording, and furtherto provide recorded matter having superior recorded images that havegood color reproducibility and reduced metamerism without conspicuousgraininess caused by dot expression.

Furthermore, it is still another object of the present invention toprovide an ink set and recording apparatus which can output bothmonochromatic and color images with a high quality, which make itpossible to obtain recorded images that are superior in terms of colorreproducibility and that have reduced metamerism without conspicuousgraininess caused by dot expression, even without using special colorinks other than YMC inks, and which make it possible to obtain a stablegray balance.

Furthermore, it is still another object of the present invention toprovide an ink set, ink jet recording method and ink jet recordingapparatus which make it possible to alleviate metamerism by means of asimple construction without any great reduction in the region of colorreproduction.

SUMMARY

As a result of diligent research, the present inventor obtained thefollowing first finding: namely, in an ink set comprising a yellow ink,magenta ink and cyan ink, even in cases where metamerism is reduced, theink set becomes superior in terms of color reproducibility (i. e., thevector balance of the three colors becomes superior) as the yellow inkapproaches the b* axis and as the magenta ink approaches the a* axis, aslong as the hue angle of the cyan ink is in the vicinity of 225 degreesto 270 degrees.

Furthermore, when the present inventor conducted further research on thebasis of this first finding, the inventor obtained the following secondfinding: namely, from the standpoint of reducing metamerism withoutcausing a drop in color reproducibility, an ink set comprising YMC inkswhich uses a magenta ink having a specified color expression, moreconcretely a magenta ink in which the Z value in the XYZ display systemstipulated by the CIE is small in cases where the Y value in the samesystem is 55 under specified conditions, makes it possible to achievethe abovementioned objects.

The present invention is based on the abovementioned second finding;this invention provides an ink set comprising a magenta ink (M) which issuch that in a case where the Y value of this ink in the XYZ displaysystem stipulated by the CIE is 55 (as calculated from theultraviolet-visible transmission spectrum of a dilute aqueous solutionof the ink with a coloring material concentration of 0.01 wt % or less),the Z value of this ink in the same system is 83 or less, and in whichthe L* value in the CIE-stipulated Lab display system of an aqueoussolution of this ink diluted 1000 times by weight is 70 or less, ayellow ink (Y) in which the L* value in the CIE-stipulated Lab displaysystem of an aqueous solution of this ink diluted 1000 times by weightis 95 or less, and a cyan ink (C) in which the L* value in theCIE-stipulated Lab display system of an aqueous solution of this inkdiluted 1000 times by weight is 70 or less (below, this invention willbe designated as the ink set of Embodiment A).

Since the ink set of the present invention comprises the abovementionedconstruction, this ink set makes it possible to obtain recorded imagesthat are superior in terms of color reproducibility, and that havereduced metamerism without any conspicuous graininess caused by dotexpression, even if no special color inks other than YMC inks are used.

Furthermore, the present invention provides a recording method forforming images using the abovementioned ink set. This recording methodmakes it possible to obtain recorded images that are superior in termsof color reproducibility, and that have reduced metamerism without anyconspicuous graininess caused by dot expression, even if no specialcolor inks other than YMC inks are used.

Furthermore, the present invention provides a recording system forforming images using the abovementioned ink set. This recording systemmakes it possible to obtain recorded images that are superior in termsof color reproducibility, and that have reduced metamerism without anyconspicuous graininess caused by dot expression, even if no specialcolor inks other than YMC inks are used.

Furthermore, the present invention provides recorded matter in whichimages are formed using the abovementioned ink set. This recorded matterhas recorded images that have a high color reproducibility, and thathave reduced metamerism without any conspicuous graininess caused by dotexpression.

As a result of diligent research, the present inventor furtherdiscovered that the abovementioned problems can also be solved, and theabovementioned objects can also be achieved, by adopting the followingconstructions:

(1) An ink set comprising a plurality of inks containing pigments ascoloring materials, wherein the plurality of inks comprise at least ayellow ink (Y), a magenta ink (M) and a cyan ink (C), the pigment in theyellow ink is C. I. pigment yellow 74, the pigment in the magenta ink isC. I. pigment violet 19, and the pigment in the cyan ink is C. I.pigment blue 15:3 (below, this invention will be designated as the inkset of Embodiment B).

(2) The ink set according to the abovementioned (1), wherein the pigmentcontent contained in the abovementioned yellow ink is 4 to 7 wt %, thepigment content contained in the abovementioned magenta ink is 4 to 7 wt%, and the pigment content contained in the abovementioned cyan ink is 3to 6 wt %.

(3) The ink set according to the abovementioned (1) or (2), wherein theink set further contains a light magenta ink (Lm) and a light cyan ink(Lc) which contain the same pigments as the abovementioned magenta inkand cyan ink, but have different color densities, the pigment containedin the light magenta ink is C. I. pigment violet 19, and the pigmentcontained in the light cyan ink is C. I. pigment blue 15:3.

(4) The ink set according to the abovementioned (3), wherein the pigmentcontent contained in the abovementioned light magenta ink is 0.5 to 2 wt%, and the pigment content contained in the abovementioned light cyanink is 0.5 to 2 wt %.

(5) The ink set according to any of the abovementioned (1) through (4),which further contains three or more types of black inks with differentpigment concentrations.

(6) The ink set according to the abovementioned (5), wherein the pigmentcontained in the abovementioned black inks is carbon black.

(7) The ink set according to the abovementioned (5) or (6), wherein theabovementioned three or more types of black inks with different pigmentconcentrations comprise a high-concentration black ink with a pigmentconcentration of 1.5 wt % or greater, a medium-concentration black inkwith a pigment concentration of 0.4 wt % to 1.5 wt %, and alow-concentration black ink with a pigment concentration of 0.01 wt % to0.4 wt %.

(8) An ink jet recording apparatus comprising the ink set according toany of the abovementioned (1) through (7).

In the present invention, furthermore, in order to solve at least someof the abovementioned problems, an ink set which is used in an ink jetprinter, and which comprises at least a magenta ink, a yellow ink and acyan ink is endowed with characteristics which are such that thespectroscopic reflectance in the spectroscopic reflectancecharacteristics of the magenta ink is 0.4 or less at at least thewavelength where the spectroscopic reflectance of the yellow ink and thespectroscopic reflectance of the abovementioned cyan ink intersect(below, this invention will be designated as the ink of Embodiment C).Furthermore, in the present specification, the term “spectroscopicreflectance of the ink” refers to the spectroscopic reflectance ofrecorded images formed by the jetting of the ink onto a recordingmedium. At the wavelength where the spectroscopic reflectance values ofthe yellow ink and cyan ink intersect, the substantially colorlessspectroscopic reflectance characteristics that are produced by themixing of the cyan ink, magenta ink and yellow ink are greater than inother wavelength regions. Consequently, metamerism is greater.Accordingly, the present invention uses a magenta ink withcharacteristics which are such that the spectroscopic reflectance ofthis ink is 0.4 or less at this wavelength. In cases where asubstantially colorless image is thus produced using a magenta ink whosespectroscopic reflectance at the abovementioned wavelength is 0.4 orless, the substantially colorless spectroscopic reflectance at thiswavelength can be suppressed, so that these substantially colorlessspectroscopic reflectance characteristics can be formed as substantiallyflat characteristics in the visible wavelength region as a whole.

Characteristics which form a wavelength region in which thespectroscopic reflectance is 0.4 or less in at least the range extendingfrom the abovementioned intersection wavelength to a wavelength of 550nm are conceivable as one example of even more desirable spectroscopicreflectance characteristics of the magenta ink. If the spectroscopicreflectance of the magenta ink is set at 0.4 or less at the wavelengthat which the spectroscopic reflectance values of the cyan ink and yellowink intersect as described above, the substantially colorlessspectroscopic reflectance characteristics can be made substantially flatthroughout the entire visible wavelength region; accordingly, suchcharacteristics are ideal. The spectroscopic reflectance characteristicsof the magenta ink used in the present invention as described above maybe taken in terms of absolute values with respect to the spectroscopicreflectance values of the cyan ink and yellow ink.

On the other hand, such spectroscopic reflectance characteristics of themagenta ink may also be taken in terms of relative values with respectto the spectroscopic reflectance characteristics of the cyan ink andyellow ink. Accordingly, an ink set which is used in an ink jet printer,and which comprises at least a magenta ink, a yellow ink and a cyan ink,is endowed with characteristics which are such that in the spectroscopicreflectance characteristics of the magenta ink at the wavelength wherethe spectroscopic distributions of the yellow ink and the abovementionedcyan ink intersect, a spectroscopic reflectance is formed that is 0.4 orless relative to the spectroscopic reflectance values of the yellow inkand cyan ink at the same wavelength (below, this invention will bedesignated as the ink set of Embodiment D). As a result, an effectsimilar to that described above (an effect that makes it possible tomake the substantially colorless spectroscopic reflectancecharacteristics substantially flat throughout the entire visiblewavelength region) can be obtained.

Characteristics which are such that the spectroscopic reflectance formsa spectroscopic reflectance that is 0.4 or less relative to thespectroscopic reflectance of the abovementioned yellow ink in at leastthe range extending from the abovementioned intersection wavelength to awavelength of 550 nm are conceivable as one example of even moredesirable spectroscopic reflectance characteristics of the magenta inkin this case. Accordingly, as one example of a magenta ink compositionwhich allows the realization of the abovementioned spectroscopicreflectance characteristics, the magenta ink is formed with acomposition that contains a styrene-acrylic acid copolymer at the rateof at least 0.7 wt %, glycerol at the rate of at least 15 wt %, ethyleneglycol at the rate of at least 5 wt %, 2-pyrrolidone at the rate of atleast 2 wt %, 1,2-hexanediol at the rate of at least 5 wt %, and anacetylene glycol type compound at the rate of at least 0.5 wt %.

As one example of a magenta ink composition that allows the realizationof spectroscopic reflectance characteristics similar to those describedabove, the magenta ink may contain one or more high-boiling-pointcompounds selected from among polyhydric alcohol type compounds andsaccharides at the rate of 5% or greater. Furthermore, the magenta inkmay contain one or more polar solvents selected from among glycol ethertype compounds and alkyldiol type compounds at the rate of 1% orgreater. Furthermore, the magenta ink may contain one or moresurfactants selected from among acetylene glycol type compounds,acetylene alcohol type compounds and polysiloxane type compounds at therate of 0.1% or greater.

Furthermore, the magenta ink may simultaneously contain one or morehigh-boiling-point compounds selected from among polyhydric alcohol typecompounds and saccharides at the rate of 5% or greater, one or morepolar solvents selected from among glycol ether type compounds andalkyldiol type compounds at the rate of 1% or greater, and one or moresurfactants selected from among acetylene glycol type compounds,acetylene alcohol type compounds and polysiloxane type compounds at therate of 0.1% or greater. Furthermore, the magenta ink may contain aresin at the rate of 0.1% or greater.

As examples of the compositions of yellow and cyan inks that aresuitable for use in the ink set of the present invention, the yellow inkis formed with a composition containing at least a styrene-acrylic acidcopolymer at the rate of 1 wt %, glycerol at the rate of 15 wt %,ethylene glycol at the rate of 5 wt %, 2-pyrrolidone at the rate of 2 wt%, 1,2-hexanediol at the rate of 5 wt %, and an acetylene glycol typecompound at the rate of 0.5 wt %. Furthermore, the cyan ink is formedwith a composition containing at least a styrene-acrylic acid copolymerat the rate of 0.5 wt %, glycerol at the rate of 15 wt %, ethyleneglycol at the rate of 5 wt %, 2-pyrrolidone at the rate of 2 wt %,1,2-hexanediol at the rate of at least 5 wt %, and an acetylene glycoltype compound at the rate of at least 0.5 wt %.

Furthermore, as examples of coloring materials of the cyan ink, yellowink and magenta ink that are suitable for use in the ink set of thepresent invention, the coloring material of the cyan ink is constructedfrom “C. I. pigment blue 15:3”, and the coloring material of the yellowink is constructed from “C. I. pigment yellow 74”; furthermore, thecoloring material of the magenta ink is constructed from “C. I. pigmentviolet 19”.

Furthermore, it goes without saying that the present invention is alsoestablished as an ink jet recording method for forming mixed-colorportions by means of a magenta ink, yellow ink and cyan ink using theink set described above, and an ink jet recording apparatus forrealizing this ink jet recording method.

Furthermore, the present invention respectively provides a recordingmethod for forming images using the abovementioned ink set, an ink jetrecording method for forming mixed-color portions by means of themagenta ink, yellow ink and cyan ink in the abovementioned ink set, arecording apparatus for realizing the abovementioned recording method,an ink jet recording apparatus comprising the abovementioned ink set, arecording system for forming images using the abovementioned ink set,and recorded matter in which images are formed using the abovementionedink set.

DESCRIPTION OF DRAWINGS

FIG. 1 is a graph which shows the relationship between C* and L* ofrecorded matter using dark magenta inks (M1 and M2) in order to evaluatethe color reproducibility of the ink set;

FIG. 2 is a graph which shows the relationship between C* and L* ofrecorded matter using light magenta inks (Lm1 and Lm2) in order toevaluate the color reproducibility of the ink set;

FIG. 3 is a graph which shows the relationships between C* and L* forthe recorded matter using both dark and light magenta inks in FIGS. 1and 2;

FIG. 4 is a diagram which shows the schematic hardware construction ofthe system constituting the printing apparatus;

FIG. 5 is a diagram which shows the schematic hardware construction ofthe printer;

FIG. 6 is a schematic structural diagram of the main control system ofthe printing apparatus realized by a computer;

FIG. 7 is a flow chart of the printing processing;

FIG. 8 is a schematic operating diagram which shows the operation thatis performed when images are printed;

FIG. 9 is an explanatory diagram which illustrates the manner in whichcolors are viewed in the human eye;

FIG. 10 is a diagram which shows the spectroscopic reflectance of theCMY inks;

FIG. 11 is a chart which shows the ink compositions;

FIG. 12 is a diagram which shows the region of color reproduction in thevicinity of L*=70;

FIG. 13 is a diagram which shows the region of color reproduction in thevicinity of L*=50; and

FIG. 14 is a flow chart which shows the processing content of the colorconversion processing.

EXPLANATION OF SYMBOLS

10 Computer, 11, 41 CPU, 12 System bus, 13, 42 ROM, 14, 43, RAM, 15 HDD,15 a Image data, 15 b LUT, 16 Flexible disk drive, 17 CD-ROM drive, 18Display, 20 OS, 21 PRTDRV, 21 a Image data acquisition module, 21 bColor conversion module, 21 c Halftone processing module, 21 d Printingdata production module, 22 Input device DRV, 23 Display DRV, 25Application program, 31 Keyboard, 32 Mouse, 40 Printer, 44 ASIC, 45Control IC, 47 a Carriage mechanism, 47 b Paper feed mechanism, 48 athrough 48 f Ink cartridges, 49 Head driving part.

DETAILED DESCRIPTION

The present invention will be described below in terms of preferredembodiments.

Embodiment A

(Ink Set)

As was described above, the ink set of Embodiment A comprises threetypes of inks (YMC inks), i. e., a specified magenta ink (M), aspecified yellow ink (Y) and a specified cyan ink (C), as essentialconstituent elements.

In the magenta ink (M) used in the present Embodiment A, in a case wherethe Y value [of this ink] in the XYZ display system stipulated by theCIE (Commission Internationale d'Eclairage) as calculated from theultraviolet-visible transmission spectrum of a dilute aqueous solutionof the ink with a coloring material concentration of 0.01 wt % or lessis 55 (for example, under the condition at a visual field angle of 2degrees with a D 65 light source), the Z value [of this ink] in the samedisplay system is 83 or less. From the standpoint of improving theeffect of the present invention, and especially from the standpoint ofachieving a greater elimination of metamerism, an ink whose Z value inthe same display system is 80 or less is desirable, and an ink whose Zvalue is 78 or less is even more desirable.

Here, for example, the abovementioned Z value can be obtained bymeasuring the transmissivity at a scanning speed of 600 nm/min, ameasurement wavelength range of 380 to 800 nm and a slit width of 2.0 nmusing a U3300 manufactured by Hitachi Seisakusho or the like, andcalculating the value at a visual field angle of 2 degrees using a D65light source (the same is true in the case of the light magenta inksdescribed later).

Furthermore, in the case of the abovementioned magenta ink, the L* valuein the CIE-stipulated Lab display system of an aqueous solution of theink diluted 1000 times by weight as stipulated is 70 or less. From thestandpoint of improving the effect of the present invention, andespecially from the standpoints of improving the coloringcharacteristics, achieving a greater elimination of metamerism andreducing the conspicuousness of graininess caused by the dot expressionsof images with an L* value of 70 to 80, an ink whose L* value in thesame display system is 50 to 70 is desirable, and an ink whose L* valueis 60 to 70 is even more desirable.

Here, for example, the abovementioned L* value can be measured bymeasuring the transmissivity at a scanning speed of 600 nm/min, ameasurement wavelength range of 380 to 800 nm and a slit width of 2.0 nmusing a U3300 manufactured by Hitachi Seisakusho or the like, andcalculating the value at a visual field angle of 2 degrees using a D65light source (the same is true in the case of other inks describedbelow).

In the case of the yellow ink (Y) used in the present Embodiment A, theL* value in the CIE-stipulated Lab display system of an aqueous solutionof the ink diluted 1000 times by weight is 95 or less. In particular,from the standpoint of being able to improve the effect of the presentinvention, and especially from the standpoint of color reproducibility,an ink whose L* value in the same display system is 70 to 95 isdesirable, and an ink whose L* value is 85 to 95 is even more desirable.

In the case of the cyan ink (C) used in the present embodiment A, the L*value in the CIE-stipulated Lab display system of an aqueous solution ofthe ink diluted 1000 times by weight is 70 or less. In particular, fromthe standpoint of being able to improve the effect of the presentinvention, and especially from the standpoints of improving the coloringcharacteristics, achieving a greater elimination of metamerism andreducing the conspicuousness of graininess caused by the dot expressionsof images with an L* value of 70 to 80, an ink whose L* value in thesame display system is 50 to 70 is desirable, and an ink whose L* valueis 60 to 70 is even more desirable.

From the standpoint of superior image fastness of the recorded matterand the like, pigments are desirable as the coloring materials (coloringagents) contained in the respective M, Y and C inks of the ink set ofEmbodiment A. Furthermore, both inorganic pigments and organic pigmentscan be used as such pigments, and these pigments may be used singly orin mixtures comprising a plurality of pigments. For example, besidestitanium oxide and iron oxide, carbon black or the like manufactured byuniversally known methods such as the contact method, furnace method,thermal method or the like may be used as the abovementioned inorganicpigments. Furthermore, azo pigments (including azo lake, insoluble azopigments, condensed azo pigments, chelate azo pigments and the like),polycyclic pigments (e. g., phthalocyanine pigments, perylene pigments,perinone pigments, anthraquinone pigments, quinacridone pigments,dioxazine pigments, thioindigo pigments, isoindolynone pigments,quinofuralone pigments and the like), dye chelates (e. g., basic dyetype chelates, acidic dye type chelates and the like), nitro pigments,nitroso pigments, aniline black and the like may be used as theabovementioned organic pigments.

In concrete terms, desired pigments may be used in accordance with theinks of the respective colors as shown below.

There are no particular restrictions on the pigment of the magenta ink,as long as the magenta ink has the [abovementioned] specified Z valueand specified L* value. For example, one or more pigments selected fromamong C. I. pigment red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 112,122, 123, 168, 184, 202, 207 and 209, C. I. pigment violet 19 and thelike may be used. In particular, C. I. pigment violet 19 is especiallydesirable, since this pigment makes it possible to obtain high-qualityimages with greatly reduced metamerism and graininess.

Furthermore, there are no particular restrictions on the pigment of theyellow ink, as long as the yellow ink has the [abovementioned] specifiedL* value. For example, one or more pigments selected from among C. I.pigment yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97,98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185and the like may be used.

Furthermore, there are no particular restrictions on the pigment of thecyan ink, as long as the cyan ink has the [abovementioned] specified L*value. For example, one or more pigments selected from among C. I.pigment blue 1, 2, 3, 15:3, 15:4, 15; 34, 16, 22 and 60, C. I. vat blue4, 60 and the like may be used.

In the case of the ink set of the present Embodiment A, in particular, acombination of YMC inks in which the pigment of the magenta ink is C. I.pigment violet 19, the pigment of the yellow ink is C. I. pigment yellow74 and the pigment of the cyan ink is C. I. pigment blue 15:3 produces amuch smoother visible absorption spectrum when mixed, and is thereforedesirable.

It is desirable from the standpoint of improving the coloringcharacteristics and the prevention of clogging that the pigment contentbe no less than 3 wt % but no more than 10 wt % in each of the Y, M andC inks. In particular, from the standpoint of reducing theconspicuousness of graininess caused by the dot expression of imageswith a high resolution (720×720 dpi), especially desirable pigmentcontents are a content of 3 to 7 wt % in the magenta ink, a content of 3to 7 wt % in the yellow ink, and a content of 3 to 7 wt % in the cyanink.

The ink set of the present Embodiment A comprises at least therespective inks described above, i. e., magenta, yellow and cyan inks;however, especially from the standpoint of reducing the conspicuousnessof graininess caused by the dot expression of images with a lowresolution (360×360 dpi), it is desirable that this ink set furthercomprise a light magenta ink (Lm) in which the L* value in theCIE-stipulated Lab display system of an aqueous solution of the inkdiluted 1000 times by weight exceeds 70.

From the standpoint of further increasing the abovementioned effect, itis even more desirable that the abovementioned L* value of the lightmagenta ink be greater than 70 but no greater than 90, and a value inthe range of 80 to 90 is especially desirable.

In addition to having the abovementioned specified L* value, it isdesirable (especially from the standpoint of improving the eliminationof metamerism) that the light magenta ink have a Z value (in the XYZdisplay system stipulated by the CIE, as calculated form theultraviolet-visible transmission spectrum of a dilute aqueous solutionof the ink with a coloring material concentration of 0.01 wt % or less)of 83 or less, preferably 80 or less, and most preferably 78 or less, ina case where the Y value of the ink in the same display system is 55.

Furthermore, there are no particular restrictions on the coloringmaterial of the light magenta ink, as long as the light magenta ink hasthe [abovementioned] specified L* value. For example, one or more of thepigments indicated as examples of pigments used in the abovementionedmagenta ink (M) may be used.

Furthermore, in regard to the pigment content in the light magenta ink,it is desirable that this content be less than 3 wt % in the lightmagenta ink, and a content of 1 wt % or greater but less than 3 wt % isespecially desirable.

It is especially desirable from the standpoint of reducing theconspicuousness of graininess caused by the dot expression of imageswith a low resolution that the ink set of the present Embodiment Afurther comprise a light cyan ink (Lc) in which the L* value in theCIE-stipulated Lab display system of an aqueous solution of the inkdiluted 1000 times by weight exceeds 70.

From the standpoint of further increasing the abovementioned effect, itis even more desirable that the abovementioned L* value of the lightcyan ink be greater than 70 but no greater than 90, and a value in therange of 80 to 90 is especially desirable.

Furthermore, there are no particular restrictions on the coloringmaterial of the light cyan ink, as long as the light cyan ink has the[abovementioned] specified L* value. For example, one or more of thepigments indicated as examples of pigments used in the abovementionedcyan ink (C) may be used.

Furthermore, in regard to the pigment content in the light cyan ink, itis desirable that this content be less than 3 wt % in the cyan ink, anda content of 0.5 to 2.5 wt % is especially desirable.

If the ink set of the present Embodiment A further comprises an ink (A)in which the L* value in the CIE-stipulated Lab display system of anaqueous solution of the ink diluted 1000 times by weight is no less than50 but no more than 80, the a* value of this aqueous solution is no lessthan 35 but no more than 85, and the b* value is no less than −5 but nomore than 55, this makes it possible to reproduce colors with a lowerlightness and higher saturation than in cases where images are formed bymixing the two colors of the magenta ink and yellow ink; accordingly,the inclusion of such an ink in the ink set is desirable from thestandpoint of further enhancing the abovementioned effect.

From the standpoint of further enhancing the abovementioned effect, itis even more desirable that the abovementioned L* value of the ink (A)be in the range of 65 to 80. Especially from the standpoint of reducingthe conspicuousness of graininess caused by the dot expression of imageswith an L* value of 70 to 80, it is desirable that the abovementioned L*value of the ink (A) be in the range of 65 to 75.

The type and content of the coloring material of the ink (A) areappropriately selected so that this ink has the abovementioned L*, a*and b* values.

For example, one or more types of coloring materials selected from amongC. I. pigment orange 5, 43 and 62, C. I. pigment red 17, 49:2, 112, 149,177, 178, 188, 255 and 264, and the like, may be used as the coloringmaterial of the ink (A).

Furthermore, in regard to the content of the coloring material in theink (A), it is desirable that this content be 1.5 to 5.5 wt %, andpreferably 2.0 to 3.0 wt %, in the ink (A).

If the ink set of the present Embodiment A further comprises an ink (B)in which the L* value in the CIE-stipulated Lab display system of anaqueous solution of the ink diluted 1000 times by weight is 20 to 60,the a* value of this aqueous solution 50 to 90 and the b* value of thisaqueous solution is −90 to −50, this makes it possible to reproducecolors with a lower lightness and a high saturation than in cases whereimages are formed by mixing the two colors of the magenta ink and cyanink. Accordingly, the inclusion of such an ink (B) in the ink set isdesirable from the standpoint of obtaining images with an even broaderrange of color reproduction.

From the standpoint of further enhancing the abovementioned effect, itis further desirable that the abovementioned L* value of the ink (B) bein the range of 30 to 50. Especially from the standpoint of reducing theconspicuousness of graininess caused by the dot expression of imageswith an L* value of 70 to 80, it is desirable that the L* value of theabovementioned ink (B) be in the range of 40 to 50.

The type and content of the coloring material of the ink (B) areappropriately selected so that this ink has the abovementioned L*, a*and b* values.

For example, one or more types of coloring materials selected from amongC. I. pigment blue 60, C. I. pigment violet 3, 19, 23, 32, 36 and 38,and the like, may be used as the coloring material of the ink (B).

Furthermore, in regard to the content of the coloring material in theink (B), it is desirable that this content be 1.0 to 7.0 wt %, andpreferably 1.5 to 3.0 wt %, in the ink (B).

The ink set of the present Embodiment A may further comprise a black ink(K) if necessary.

Examples of coloring materials that can be used in such a black inkinclude inorganic pigments such as carbon black (C.I. pigment black 7),e. g., furnace black, lamp black, acetylene black, channel black or thelike, iron oxide pigments or the like, and organic pigments such asaniline black (C. I. pigment black 1) or the like. Among these pigments,the use of carbon black is especially desirable. Desirable examples ofcarbon black include No. 2300, NO. 900, MCF88, No. 33, No. 40, No. 45,No. 52, MA7, MA8, MA100, No. 2200B and the like manufactured byMitsubishi Kagaku, Raven5750, Raven5250, Raven5000, Raven3500,Raven1255, Raven700 and the like manufactured by Columbia Co., Regal400R, Regal 1660R, Mogul L, Monarch 700, Monarch 800, Monarch 880,Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 andthe like manufactured by Cabot Co., and Color Black FW1, Color BlackFW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color BlackS150, Color Black S160, Color Black S170, Printex 35, Printex U, PrintexV, Printex 140U, Special Black 6, Special Black 5, Special Black 4A,Special Black 4 and the like manufactured by Degussa Co.

The content of the pigment in the black ink is preferably 0.1 to 10.0 wt%, and is even more preferably 1.0 to 8.0 wt %.

Furthermore, in addition to the abovementioned inks, the ink set of thepresent Embodiment A may contain one or more other inks such as lightblack inks, transparent inks, white inks or the like.

It is desirable that the respective inks of the ink set of the presentEmbodiment A use pigments as coloring materials, and that these inkscontain dispersing agents used to disperse the pigments. Dispersingagents similar to those used in [conventional] pigment inks of this typecan be used without any particular restrictions as dispersing agents [inthe present invention]. For example, cationic dispersing agents, anionicdispersing agents, nonionic dispersing agents or surfactants and thelike may be used. Examples of anionic dispersing agents that can be usedinclude polyacrylic acids, polymethacrylic acids, acrylicacid-acrylonitrile copolymers, vinyl acetate-acrylic acid estercopolymers, acrylic acid-acrylic acid alkyl ester copolymers,styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers,styrene-acrylic acid-acrylic acid alkyl ester copolymers,styrene-methacrylic acid-acrylic acid alkyl ester copolymers,styrene-α-methylstyrene-acrylic acid copolymers,styrene-α-methylstyrene-acrylic acid-acrylic acid alkyl estercopolymers, styrene-maleic copolymers, vinyinaphthalene-maleic acidcopolymers, vinyl acetate-ethylene copolymers, vinyl acetate-fatty acidvinylethylene copolymers, vinyl acetate-maleic acid ester copolymers,vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acidcopolymers and the like. Furthermore, examples of anionic surfactantsthat can be used include sodium dodecylbenzenesulfonate, sodium laurate,ammonium salts of polyoxyethylene alkyl ether sulfates and the like, andexamples of nonionic surfactants that can be used includepolyoxyethylene alkyl ethers, polyoxyethylene alkyl esters,polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl phenylethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides and thelike. These compounds may be used singly or in combinations of two ormore compounds. In particular, from the standpoint of increasing thedispersion stability of the pigments, it is desirable to usestyrene-(meth)acrylic acid copolymers.

The abovementioned dispersing agents are ordinarily contained in theabovementioned respective inks at the rate of 140 wt % or less(calculated as solid content), with the weights of the abovementionedpigments as a standard.

Furthermore, in the abovementioned inks such as the magenta ink, yellowink, cyan ink, light magenta ink, light cyan ink, ink (A), ink (B) andthe like, the abovementioned dispersing agents are preferably containedin the inks at the rate of 10 to 140 wt % (more preferably at the rateof 10 to 100 wt %, and even more preferably at the rate of 20 to 40 wt%) calculated as solid content, with the weights of the abovementionedpigments as a standard.

Furthermore, the contents of the dispersing agents with respect to theamounts of the respective inks are preferably 0.1 to 10 wt %, and evenmore preferably 0.3 to 6 wt %, calculated as solid content.

Furthermore, in cases where the respective inks of the ink set of thepresent Embodiment A are used in ink jet recording, it is desirable fromthe standpoint of preventing clogging of the ink jet printer head (bypreventing drying of the ink) that these inks contain ahigh-boiling-point organic solvent. Examples of high-boiling-pointorganic solvents that can be used include polyhydric alcohols such asethylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, polypropylene glycol, propylene glycol, butylene glycol,1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerol,trimethylolethane, trimethylolpropane and the like; alkyl ethers ofpolyhydric alcohols such as ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, diethylene glycol monobutyl ether, triethyleneglycol monomethyl ether, triethylene glycol monoethyl ether, triethyleneglycol monobutyl ether and the like; urea, 2-pyrrolidone,N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolinone, organic alkaliessuch as triethanolamine and the like, and saccharides such as sugaralcohols and the like. These solvents may be used singly or incombinations of two or more solvents. In particular, the addition of anorganic alkali such as triethanolamine or the like together withglycerol improves the prevention of clogging, stabilizes thedispersibility of the coloring material, and improves the glossiness ofrecorded images, and is therefore desirable.

The abovementioned high-boiling-point organic solvents are preferablycontained in the abovementioned respective inks at the rate of 0.1 to 30wt %, and are even more preferably contained at the rate of 0.5 to 20 wt%.

Furthermore, among these high-boiling-point solvents, triethanolaminehas the functions of a pH adjusting agent and dispersion stabilizingagent for the inks; accordingly, from the standpoint of achieving afavorable manifestation of these functions, it is desirable to use thistriethanolamine in the range of 0.1 to 10 wt % in the respective inks.

Furthermore, from the standpoint of increasing the ink permeability byincreasing the wettability on the recording medium, the respective inksof the ink set of the present Embodiment A may contain a permeationpromoting agent. Examples of permeation promoting agents that can beused include alcohols such as methanol, ethanol, iso-propyl alcohol andthe like; lower alkyl ethers of polyhydric alcohols such as ethyleneglycol monomethyl ether, diethylene glycol monoethyl ether, diethyleneglycol monobutyl ether, triethylene glycol monobutyl ether, propyleneglycol monobutyl ether, dipropylene glycol monobutyl ether and the like;and diols such as 1,2-pentanediol, 1,2-hexanediol and the like. Thesecompounds may be used singly or in combinations of two or morecompounds. It is especially desirable to use diethylene glycol monobutylether, triethylene glycol monobutyl ether or 1,2-hexanediol.

The abovementioned permeation promoting agent is preferably contained inthe abovementioned inks at the rate of 1 to 20 wt %, and is even morepreferably contained at the rate of 1 to 10 wt %.

Furthermore, from the standpoint of increasing the ink permeability byincreasing the wettability on the recording medium in the same manner asin the case of the abovementioned permeation promoting agents, therespective inks of the ink set of the present Embodiment A may also usevarious types of surfactants such as anionic surfactants, nonionicsurfactants, cationic surfactants, amphoteric surfactants and the like.In particular, the use of acetylene glycol type compounds or siliconetype compounds is especially desirable. Commercially marketed compoundsmay be used as these acetylene glycol type compounds. Examples ofcompounds that can be used include Olfin Y, Surfynol 82, 440, 465, 485,STG, E1010 (all commercial names of products manufactured by AirProducts and Chemicals Inc.) and the like. These compounds may be usedsingly or in combinations of two or more compounds. In particular, it isespecially desirable to use E1010 or Surfynol 465. Furthermore, inregard to commercially marketed products, polysiloxane type compoundssuch as BYK348 (manufactured by BYK-Chemie Japan) and the like can beused as the abovementioned silicone type compounds. The content of suchacetylene glycol type compounds and/or the abovementioned silicone typecompounds in the abovementioned inks is preferably 0.01 to 5 wt %, evenmore preferably 0.1 to 1.0 wt %, and most preferably 0.1 to 0.5 wt %.

Furthermore, from the standpoint of shortening the ink drying time, therespective inks of the ink set of the present Embodiment A may contain alow-boiling-point solvent. Examples of such low-boiling-point solventsthat can be used include methanol, ethanol, n-propyl alcohol, iso-propylalcohol, n-butanol, sec-butanol, tert-butanol, iso-butanol, n-pentanoland the like. These solvents may be used singly or in combinations oftwo or more solvents. Monohydric alcohols are especially desirable.

The respective inks of the ink set of the present Embodiment A containcomponents such as the abovementioned pigments, dispersing agents,high-boiling-point solvents, permeation promoting agents, acetyleneglycol type compounds and/or silicone type compounds and the like, andordinarily contain water as the balance. It is desirable to use purewater or ultra-pure water such as ion exchange water, ultra-filteredwater, reverse osmosis water, distilled water or the like as this water.In particular, water produced by subjecting these types of water to asterilization treatment using ultraviolet irradiation, addition ofhydrogen peroxide or the like makes it possible to prevent thegeneration of mold and bacteria over a long period of time, and istherefore desirable.

If necessary, the respective inks of the ink set of the presentEmbodiment A may also contain other additives, e. g., fixing agents suchas water-soluble rosins or the like, anti-mold agents or preservativessuch as sodium benzoate or the like, antioxidants or ultravioletabsorbing agents such as allophanates or the like, chelating agents,oxygen absorbing agents, pH adjusting agents and the like. Theseadditives may be used singly or in combinations of two or moreadditives.

The respective inks of the ink set of the present Embodiment A can beprepared in the same manner as conventional pigment inks using aconventional universally known apparatus, e. g., a ball mill, sand mill,attriter, basket mill, roll mill or the like. In the preparation ofthese inks, it is desirable to remove coarse particles using a membranefilter, mesh filter or the like.

There are no particular restrictions on the use of the ink set of thepresent Embodiment A; however, it is desirable that this ink set be usedin an ink jet recording method which is a recording method in whichliquid droplets of ink are caused to jet from nozzles, and these liquiddroplets are caused to adhere to a recording medium, so that images suchas characters, figures or the like are formed, and it is especiallydesirable that this ink set be used in an on-demand type ink jetrecording method. Examples of on-demand type ink jet recording methodsinclude piezoelectric element recording methods in which recording isperformed using piezoelectric elements that are disposed in a printerhead, hot jet recording methods in which recording is performed usingthermal energy created by heaters such a heat-generating resistanceelements or the like disposed in a printer head, and other similarrecording methods. The ink set of the present Embodiment A can beappropriately used in any of these ink jet recording methods.

Furthermore, in cases where the ink set of the present Embodiment A isused in an ink jet recording method as described above, the reliabilityof this ink set as an ink set for use in ink jet recording is high, andin particular, the reliability as an ink set for use in ink jetrecording can be increased even further (in spite of the fact that thecolor reproducibility is broad) by setting the respective inks in theink set at pigment concentrations that do not cause clogging of thenozzles of the ink jet printer or the like.

In regard to the recording medium used to form images, the ink set ofthe present Embodiment A can be used without restrictions on recordingmedia that are ordinarily used in ink jet recording methods and thelike; however, this ink set is ideally used on media that have a coatinglayer or on ordinary paper (recording media in which fibers are exposedat the surface on which recording is performed). In particular, if theink set of the present Embodiment A is used on media that have a coatinglayer, a considerable suppression of the conspicuousness of graininesscaused by dot expression when images are formed can be achieved.

In the present specification, the term “media that have a coating layer”refers to all media in which the surface on which images are formed (thesurface on which recording is performed) using the abovementioned inkset is covered by at least a coating layer. Ordinarily, media that havean 85-degree luster of 120 or less are used as such media that have acoating layer. Here, the 85-degree luster is measured using a “PG1M”manufactured by Nippon Denshoku Kogyo K.K. or the like. Furthermore, inthese measurements, the measuring apparatus is adjusted beforehand sothat the 85-degree luster of a standard luster plate shows a value of100.

Examples of media that have a coating layer include mirror surface tonemedia in which the 85-degree luster is 70 to 120, e. g., media whichhave a resin coating layer that allows naked-eye confirmation of thesilhouette of a duplicate image of a fluorescent lamp in cases wherelight from such a fluorescent lamp is directed onto the medium from adistance of 1 m or greater (or the like). A typical example of such amedium is “PGPP (Premium Glossy Photo Paper)” manufactured bySeiko-Epson Co., which has an 85-degree luster of 81.

Furthermore, other examples of media that have a coating layer includesemi-gloss tone media which have an 85-degree luster of 10 to 70, mattetone media which have an 85-degree luster of 10 or less, and the like.

Furthermore, the ink set of the present Embodiment A makes it possibleto achieve an extreme suppression of graininess caused by dot expressioneven in the case of recording at a high resolution on relativelysmall-size media (preferably media that have a coating layer) such as Lsize or the like. Accordingly, the ink set of the present Embodiment Ais especially useful on relatively small-size media such as L size orthe like.

(Recording Method)

Next, the recording method of the present invention will be described.

The present invention can provide a recording method for forming imagesusing the abovementioned ink set, i. e., an embodiment of a recordingmethod for forming images using an ink set comprising at least a magentaink (M) having the abovementioned specified Z value and L* value, ayellow ink (Y) having the abovementioned specified L* value, and a cyanink (C) having the abovementioned specified L* value; in particular, arecording method using the ink set of the abovementioned embodiment isespecially suitable. Furthermore, in all respects other than the use ofthe abovementioned ink set, the recording method of the presentinvention can be performed in the same manner as an ordinary ink jetrecording method.

In particular, an ink jet recording method in which liquid droplets ofthe abovementioned inks of a plurality of colors are respectively causedto jet, and which is devised so that in cases where one color(monochrome) among the abovementioned YMC is formed on the recordingmedium, an image is formed by the ink corresponding to this color, andso that in cases where mixed color portions of secondary colors orgreater (colors that cannot be formed using YMC inks singly), thesemixed color portions are formed by at least two types of inks among theYMC inks, can be suitably provided. Furthermore, images with a greatlyimproved color reproducibility can be obtained by an ink jet recordingmethod in which such mixed color portions are formed by at least twotypes of inks among the YMC inks, and the [abovementioned] Lm ink, Lcink, ink (A) and/or ink (B). Furthermore, an ink jet recording method inwhich such mixed color portions are formed by a black ink (K) inaddition to the abovementioned inks can be provided.

In the recording method of the present embodiment, it is desirable thatimages be formed so that the ink weight at a duty of 100% is 7 to 13mg/inch².

Furthermore, in the case of mixed colors, it is desirable that images beformed so that the ink weight at a duty of 120% is 8 to 16 mg/inch².

Furthermore, in the present specification, the term “duty” refers tounits of the value D defined and calculated by the following equation:D=[actual number of printed dots/(vertical resolution×horizontalresolution)]×100

Furthermore, the term “duty of 100%” refers to the maximum ink weightfor a single color per pixel.

(Recording System)

The present invention can provide an embodiment of a recording systemfor forming images using the abovementioned ink set. In particular, arecording apparatus such as an ink jet printer or the like (or someother recording system) using the ink set of the abovementionedembodiment is especially suitable.

(Recorded Matter)

The present invention can provide an embodiment of recorded matter inwhich images are formed using the abovementioned ink set. In particular,recorded matter using the ink set of the abovementioned embodiment isespecially suitable.

Embodiment B

As was described above, the ink set of Embodiment B comprises threetypes of inks (YMC inks), i. e., a specified yellow ink (Y), a specifiedmagenta ink (M) and a specified cyan ink (C), as essential constituentelements.

The abovementioned ink set makes it possible to obtain high-qualityimages in which metamerism is reduced by means of a combination of YMCin which the pigment in the yellow ink is C. I. pigment yellow 74, thepigment in the magenta ink is C. I. pigment violet 19, and the pigmentin the cyan ink is C. I. pigment 15:3.

From the standpoint of coloring characteristics and the permissiblelevel of graininess at a high resolution, it is desirable that thecontents of the pigments in the abovementioned inks be 3 wt % or greaterin the respective Y, M and C inks. Especially desirable pigment contentsare 4 to 7 wt % in the yellow ink, 4 to 7 wt % in the magenta ink, and 3to 6 wt % in the cyan ink.

Furthermore, in regard to the pigment contents in the abovementioned inkset, it is desirable from the standpoint of allowing images with animproved hue to be obtained that the content of the abovementioned cyanpigment in the cyan ink be smaller than the respective contents of theabovementioned yellow pigment and magenta pigment in the yellow ink andmagenta ink.

The ink set of the present Embodiment B comprises the abovementionedrespective inks, i. e., the abovementioned yellow, magenta and cyaninks; however, it is desirable from the standpoint of alleviatinggraininess at a low resolution that this ink set further comprise alight magenta ink (Lm).

From the standpoints of reducing graininess and metamerism at a lowresolution, C. I. pigment violet 19 is desirable as the coloringmaterial of this light magenta ink.

Furthermore, it is desirable that the content of the pigment in thelight magenta ink be less than 3 wt %, and a content of 0.5 to 2 wt % isespecially desirable.

It is desirable from the standpoint of alleviating graininess at a lowresolution that the ink set of the present Embodiment B further comprisea light cyan ink (Lc).

From the standpoints of reducing graininess and metamerism at a lowresolution, C. I. pigment blue 15:3 is desirable as the coloringmaterial of this light cyan ink.

Furthermore, it is desirable that the content of the pigment in thelight cyan ink be less than 3 wt %, and a content of 0.5 to 2 wt % isespecially desirable.

Furthermore, it is desirable from the standpoints of improving thequality of monochromatic images, improving the halftone properties ofportions with a low lightness, and stabilizing the gray balance so thatvariation in this balance is reduced, that the ink set of the presentEmbodiment B further comprise two or more, and preferably three or more,black inks with different pigment concentrations.

In a case where the abovementioned black inks with different pigmentconcentrations are divided into three groups, i. e., high-concentrationblack inks with a carbon black concentration of 1.5 wt % or greater,medium-concentration black inks with a carbon black concentration of 0.4wt % or greater but less than 1.5 wt %, and low-concentration black inkswith a carbon black concentration of 0.01 wt % or greater but less than0.4 wt %, it is desirable that the black inks be equally selected fromthe different groups.

For example, carbon black manufactured by universally known methods suchas the contact method, furnace method, thermal method or the like can beused as the carbon black contained in the black inks. In concrete terms,carbon black similar to that cited as examples of the carbon blackdesirable for use in the abovementioned ink set of Embodiment A, i. e.,various types of carbon black including No. 2300 or the likemanufactured by Mitsubishi Kagaku, can be used.

In the same ink set, the carbon black contained in the respective blackinks may be the same or different types of carbon black.

Furthermore, in addition to the abovementioned inks, the ink set of thepresent Embodiment B may also comprise one or more other inks such astransparent inks, white inks or the like.

It is desirable that the respective inks of the present Embodiment B usepigments as coloring materials, and that these inks contain dispersingagents used to disperse these pigments. The types and contents of thedispersing agents are similar to those used in the abovementionedEmbodiment A.

In particular, in the inks of the present Embodiment B, it is desirablethat the abovementioned dispersing agents be contained at the rate of 20to 80 wt %, preferably 25 to 60 wt % (calculated as solid content), withthe weights of the abovementioned pigments as a standard.

Furthermore, for the same reasons as in Embodiment A, it is desirablethat the respective inks of the ink set of the present Embodiment Bcontain a high-boiling-point solvent. The types and contents of suchhigh-boiling-point solvents are similar to those used in theabovementioned Embodiment A.

Furthermore, for the same reasons as in Embodiment A, the respectiveinks of the ink set of the present Embodiment B may contain permeationpromoting agents, various types of surfactants, low-boiling-pointsolvents, water, other additives and the like. The types and contents ofthese additives are similar to those used in the abovementionedEmbodiment A.

In particular, examples of acetylene glycol type compounds that may beused as surfactants include Olfin E1010, STG, Y (all commercial names ofproducts manufactured by Nisshin Kagaku K.K.), Surfynol 82, 104, 440,465, 485 (all commercial names of products manufactured by Air Productsand Chemicals Inc.) and the like. These compounds may be used singly orin combinations of two or more compounds. In particular, the use ofE1010 or Surfynol 465 is especially desirable. Furthermore, in regard tothe abovementioned silicone type compounds, compounds expressed by thefollowing general formula (1) or the like may be used as commerciallymarketed products.

In the above formula, R¹ through R⁷ each independently indicate a C₁₋₆alkyl group, preferably a methyl group, and j, k and g eachindependently indicate an integer of 1 or greater, preferably 1 to 5,more preferably 1 to 4, and even more preferably 1 or 2. EO indicates anethyleneoxy group, and PO indicates a propyleneoxy group. p and qindicate integers of 0 or greater, preferably 1 to 5, with p+qindicating an integer of 1 or greater, preferably 2 to 4. Within thebrackets, EO and PO may be in any order, and may be random or in blocks.

In a desirable aspect of the present Embodiment B, a compound thatsatisfies the condition j=k=g=1 to 3 (preferably 1 or 2) is desirable asthe compound of formula (1).

Furthermore, in another desirable aspect of the present Embodiment B, acompound in which R¹ through R⁷ are all methyl groups, j=k=g=1, p is aninteger of 1 or greater (preferably 1 to 5), and q indicates 0, isdesirable as the compound of formula (1).

Compounds expressed by general formula (1) are commercially marketed,and such [commercially marketed] compounds may be used. For example, thesilicone type surfactants BYK-345, BYK-346, BYK-347, BYK-348 and thelike of BYK-Chemie Japan are desirable.

The abovementioned acetylene glycol type compounds and/or theabovementioned silicone type compounds are preferably contained in theabovementioned inks at the rate of 0.01 to 5 wt %, and a content of 0.1to 1.0 wt % is even more desirable.

Furthermore, the inks of the present Embodiment B may also contain finepolymer particles (i. e., a resin emulsion). Moreover, the term“emulsion” refers to an aqueous dispersion of such fine polymerparticles in which the dispersion medium is water and the dispersedsubstance comprises fine polymer particles.

From the standpoint of improving luster and improving the stability ofthe recorded images, it is desirable that the inks of the presentEmbodiment B contain three types of emulsions, i. e., (i) a polymercontaining sulfonic acid groups (sol type resin), (ii) a modifiedpolypropylene emulsion, and (iii) an alkali-soluble emulsion.

(i) Resin Emulsion (1)

It is desirable that the abovementioned polymer containing sulfonic acidgroups be a diene type sulfonic-acid-group-containing polymer and/or anon-diene type sulfonic-acid-group-containing polymer.

The abovementioned polymer containing sulfonic acid groups is a polymerobtained by subjecting a polymer or copolymer obtained by thehomopolymerization or copolymerization of the monomers shown below to asulfonation treatment (Japanese Patent Application Laid-Open No.11-217525), or a polymer obtained by the homopolymerization orcopolymerization of sulfonated monomers. Such polymers include dienetype sulfonic-acid-group-containing polymers in which diene typemonomers are essential components, and non-diene typesulfonic-acid-group-containing monomers in which diene type monomers arenot essential components.

Monomers that can be used in order to obtain the abovementioned dienetype sulfonic-acid-group-containing polymers include diene type monomersand other monomers that can be used in combination with diene typemonomers.

Examples of diene type monomers include diene type compounds with 4 to10 carbon atoms, e. g., 1,3-butadiene, 1,2-butadiene, 1,3-pentadiene,1,2-pentadiene, 2,3-pentadiene, isoprene, 1,2-hexadiene, 1,3-hexadiene,1,4-hexadiene, 1,5-hexadiene, 2,3-hexadiene, 2,4-hexadiene,2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,2-heptadiene,1,3-heptadiene, 1,4-heptadiene, 1,5-heptadiene, 1,6-heptadiene,2,3-heptadiene, 2,5-heptadiene, 3,4-heptadiene, 3,5-heptadiene,cyclopentadiene and the like. These diene type monomers can be usedsingly or in combinations of two or more monomers.

Examples of other monomers that can be used in combination with dienetype monomers include aromatic monomers such as styrene,α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene,vinyinaphthalene and the like, (meth)acrylic acid alkyl esters such asmethyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate andthe like, mono- or dicarboxylic acids or dicarboxylic acid anhydridessuch as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid orthe like, vinylcyan compounds such as (meth)acrylonitrile and the like,and unsaturated compounds such as vinyl chloride, vinylidene chloride,vinyl methyl ethyl ketone, vinyl acetate, (meth)acrylamide, glycidyl(meth)acrylate and the like. These other monomers may be used single orin combinations of two or more monomers. In cases where these othermonomers are used in combination, the amount of diene type monomers usedis preferably 0.5 wt % or greater, more preferably 1 wt % or greater,and even more preferably 5 wt % or greater.

The diene type copolymers obtained by copolymerizing the abovementioneddiene type monomers or other monomers that can be used in combinationwith diene type monomers may be copolymers of any type, including randomcopolymers and block copolymers.

Examples of desirable polymers include isoprene homopolymers, butadienehomopolymers, isoprene-styrene random copolymers, isoprene-styrene blockcopolymers, styrene-isoprene-styrene tertiary block copolymers,butadiene-styrene random copolymers, butadiene-styrene block copolymers,styrene-butadiene-styrene block copolymers, styrene-butadiene-styrenetertiary block copolymers, ethylene-propylene-diene tertiary blockcopolymers and the like. Examples of even more desirable copolymersisoprene-styrene block copolymers, styrene-isoprene-styrene tertiaryblock copolymers, butadiene-styrene block copolymers,styrene-butadiene-styrene block copolymers, styrene-butadiene-styrenetertiary block copolymers and the like.

The diene type sulfonic-acid-group-containing polymers used in thepresent Embodiment B may be polymers in which the abovementioned dienetype polymers and/or polymers obtained by partially or completelyhydrogenating the residual double bonds based on precursor monomers ofthe same are sulfonated by a universally known sulfonation method, e.g., one of the methods described in Nippon Kagakukai (ed.), Shin-JikkenKagaku Koza [New Experimental Chemistry Lectures] (Vol. 14, 111. p.1773), Japanese Patent Application Laid-Open No. 2-227403 or the like.

Examples of sulfonating agents that can be used include sulfuricanhydride, sulfuric acid, chlorosulfonic acid, fuming sulfuric acid,hydrogensulfites (salts of Li, Na, K, Rb, Cs or the like) or the like.The amount of sulfonating agent used is preferably 0.005 to 1.5 moles,and even more preferably 0.01 to 1.0 moles, per mole of theabovementioned polymers (calculated as sulfuric anhydride).

Next, it is desirable that the abovementioned diene typesulfonic-acid-group-containing polymers be used in a state obtained bycausing water and/or a basic compound to act on the product obtained bysulfonation as described above. examples of basic compounds that can beused include alkali metal hydroxides, alkali metal alkoxides, alkalimetal carbonates, aqueous ammonia, organo-metallic compounds, amines andthe like. Such basic compounds may be used singly or in combinations oftwo or more compounds. The amount of such basic compounds used is 2moles or less, preferably 1.3 moles or less, per mole of sulfonatingagent used.

Examples of monomers that can be used to obtain non-diene typesulfonic-acid-group-containing polymers include monomers that havesulfonyl groups, e. g., vinyl monomers such as allylsulfonic acid,vinylsulfonic acid or methacrylsulfonic acid obtained by reactingisobutylene and sulfur trioxide, styrene type monomers such as sodiump-styrenesulfonate or the like (e. g., Spiromer manufactured by ToyoSoda K.K.), or methacrylic acid ester type monomers expressed by thegeneral formula CH₂═C(CH₃)—COO(AO)_(n)SO₃Na (A: lower alkylene group)(e. g., Eleminol RS-30 manufactured by San'yo Kasei K.K.), and sodiumsalts, potassium salts or lithium salts of the abovementioned monomersor the like.

Such non-diene type sulfonic-acid-group-containing polymers can also beobtained by copolymerizing monomers that do not contain sulfonic acidgroups with the abovementioned monomers that have sulfonic acid groups.

Examples of other copolymerizable monomers include aromatic monovinylcompounds such as styrene, ethylvinylbenzene, α-methylstyrene,fluorostyrene, vinylpyrine and the like, acrylic acid ester monomerssuch as butyl acrylate, 2-ethylhexyl acrylate,β-methacryloyloxyethylhydrodiene phthalate, N,N′-dimethylaminoethylacrylate and the like, methacrylic acid ester monomers such as2-ethylhexyl methacrylate, methoxydiethylene glycol methacrylate,methoxypolyethylene glycol methacrylate, methyl methacrylate, ethylmethacrylate, butyl methacrylate, N,N′-dimethylaminoethyl methacrylate,glycidyl methacrylate and the like, vinyl cyanide compounds such asacrylonitrile, methacrylonitrile and the like, silicone-modifiedmonomers, macromonomers and the like. Furthermore, conjugate double bondcompounds such a butadiene, isoprene and the like, vinyl ester compoundssuch as vinyl acetate and the like, and 4-methyl-1-pentene and otherα-olefin compounds may also be cited. Among these copolymerizablemonomers, styrene, methyl methacrylate and acrylonitrile are especiallydesirable. The amount of such copolymerizable monomers used isordinarily 1 to 93 wt %, and preferably 5 to 80 wt %, of thepolymerizable monomer(s) used.

Such non-diene type sulfonic-acid-group-containing polymers can bepolymerized by subjecting the abovementionedsulfonic-acid-group-containing monomers orsulfonic-acid-group-containing monomers and other copolymerizablemonomers to radical polymerization using a radical polymerizationinitiator, chain transfer agent or the like in a solvent used forpolymerization such as water, an organic solvent or the like.

The abovementioned non-diene type sulfonic-acid-group-containingpolymers obtained by copolymerizing the abovementioned non-diene typemonomers may be copolymers of any type including random copolymers andblock copolymers. In particular, acrylic typesulfonic-acid-group-containing polymers are especially desirable asnon-diene type sulfonic-acid-group containing polymers.

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the abovementioned finepolymer particles have an acid value of 100 or greater.

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the abovementioned finepolymer particles have a weight average molecular weight (Mw) of no lessthan 8,000 but no more than 20,000, and a glass transition temperature(Tg; measured according to JIS K6900) of no less than 5° C. but not morethan 50° C.

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the minimum film formingtemperature (MFT) of the abovementioned fine polymer particles be 20° C.or less.

It is desirable that the particle size of the abovementioned finepolymer particles be 70 nm or less. Even more preferably, this particlesize is no less than 20 nm but no more than 70 nm. If the size of thefine polymer particles is within this range, the fine polymer particlescan easily form an emulsion in water, so that inks with a high stabilityare obtained, and high-quality recorded images are obtained.

(ii) Resin Emulsion (2)

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the abovementionedpolypropylene emulsion be an emulsion obtained by modifying apolypropylene with a weight average molecular weight (Mw) of no lessthan 1,000 but no more than 50,000 with an unsaturated carboxylic acidor anhydride of the same, and then dispersing this modifiedpolypropylene in water in the presence of a basic compound and anemulsifier.

It is desirable that the abovementioned unsaturated carboxylic acid bemaleic acid and/or maleic anhydride.

Examples of modified polypropylene emulsions that can be used in thepresent Embodiment B include emulsions obtained by modifying alow-molecular-weight polypropylene by a universally known method using aheated reaction or an organic peroxide. For example, such an emulsion isobtained as follows: namely, in an inert gas atmosphere, alow-molecular-weight polypropylene is heated and dissolved in thepresence of an aromatic solvent or a chlorine type solvent, or in thepresence of a peroxide radical generating catalyst, and is modified bygrafting an unsaturated carboxylic acid or an anhydride of the same.

For example, AQUACER593 (commercial name of a product manufactured byBYK-Chemie Japan) or the like can be used as such a modifiedpolypropylene emulsion.

(iii) Resin Emulsion (3)

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the abovementionedalkali-soluble emulsion be an emulsion that is formed by the colloidaldispersion of an acrylic resin in the ink.

It is desirable that this acrylic resin be a copolymer obtained bypolymerizing an ethylenic unsaturated carboxylic acid monomer andanother monomer that is copolymerizable with this monomer in thepresence of a water-soluble macromolecular compound containing alcoholichydroxy groups or a copolymerizable surfactant.

Examples of the abovementioned ethylenic unsaturated carboxylic acidmonomers include ethylenic unsaturated monocarboxylic acid monomers suchas acrylic acid, methacrylic acid and the like; ethylenic unsaturatedpolyhydric carboxylic acid monomers such as itaconic acid, maleic acid,fumaric acid, butenetricarboxylic acid and the like; ethylenicunsaturated polyhydric carboxylic acid partial ester monomers such asmonobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate andthe like; and polyhydric carboxylic acid anhydrides such as maleicanhydride, citraconic anhydride and the like.

Examples of other monomers that can be copolymerized with theabovementioned ethylenic unsaturated carboxylic acid monomers includearomatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene,chlorostyrene and the like; (meth)acrylic acid ester monomers such asmethyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,n-amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate,ethylhexyl (meth)acrylate, octyl (meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylateand the like; cyano-group-containing ethylenic unsaturated monomers suchas (meth)acrylonitrile and the like; ethylenic unsaturated glycidylether monomers such as allyl glycidyl ether and the like; ethylenicunsaturated amide monomers such as (meth)acrylamide,N-methylol(meth)acrylamide, N-butoxymethyl(meth)acrylamide and the like;conjugate diene monomers such as 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like; and carboxylicacid vinyl ester monomers such as vinyl acetate and the like.

Water-soluble macromolecular compounds containing 5 to 25 alcoholichydroxy groups per 1000 units of molecular weight are desirable as theabovementioned water-soluble macromolecular compounds containingalcoholic hydroxy groups; examples of such macromolecular compoundsinclude vinyl alcohol type polymers such as polyvinyl alcohols, varioustypes of modified polyvinyl alcohols and the like; saponified copolymersof vinyl acetate with acrylic acid, methacrylic acid or maleicanhydride; cellulose derivatives such as alkylcelluloses,hydroxyalkylcelluloses, alkylhydroxyalkylcelluloses and the like; starchderivatives such as alkyl starches, carboxymethyl starches and the like;and other compounds such as gum arabic, traganth gum, polyalkyleneglycols and the like.

The abovementioned copolymerizable surfactants are surfactants that haveone or more polymerizable vinyl groups per molecule; examples of suchsurfactants include anionic polymerizable surfactants such as sodiumpropenyl-2-ethylhexylsulfosuccinic acid ester, (meth)acrylic acidpolyoxyethylene sulfuric acid ester, polyoxyethylene alkylpropenyl ethersulfuric acid ester ammonium salts, (meth)acrylic acid polyoxyethyleneester phosphoric acid esters and the like; and anionic polymerizablesurfactants such as polyoxyethylene alkylbenzene ether (meth)acrylicacid esters, polyoxyethylene alkyl ether (meth)acrylic acid esters andthe like.

From the standpoints of improving luster and improving the stability ofthe recorded images, the weight average molecular weight (Mw) of thealkali-soluble resin in the abovementioned alkali-soluble emulsion ispreferably no less than 8,000 but no more than 20,000, and is even morepreferably no less than 9,000 but no more than 10,000.

From the standpoints of improving luster and improving the stability ofthe recorded images, the acid value of the alkali-soluble resin in theabovementioned alkali-soluble emulsion is preferably 40 mg KOH/G orless.

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the abovementionedalkali-soluble resin be caused to form an emulsion by colloidaldispersion in the ink after the pH has been adjusted to a value of 8 to11 (preferably a pH value of 9 to 10) by means of an inorganic base suchas an alkali metal hydroxide, alkaline earth metal hydroxide or thelike.

From the standpoints of improving luster and improving the stability ofthe recorded images, it is desirable that the content of theabovementioned fine polymer particles in the respective inks be no lessthan 0.05 wt % but no more than 10.0 wt %. This content is morepreferably no less than 0.1 wt % but no more than 5.0 wt %, and is evenmore preferably no less than 0.1 wt % but no more than 2.0 wt %.Furthermore, the weight of the fine polymer particles referred to hereis the weight calculated in terms of the solid content.

A single type of fine polymer particles may be added, or two or moretypes of such particles may be mixed and added. In cases where suchparticles are mixed and added, the total content of the particles in theink is preferably no less than 0.05 wt % but no more than 10.0 wt %,more preferably no less than 0.1 wt % but no more than 5.0 wt % (andeven more preferably no less than 0.1 wt % but no more than 2.0 wt %).

The respective inks of the ink set of the present Embodiment B can beprepared in the same manner as conventional pigment inks using aconventional universally known apparatus, e. g., a ball mill, sand mill,aftriter, basket mill, roll mill or the like. In the preparation ofthese inks, it is desirable to remove coarse particles using a membranefilter, mesh filter or the like.

It is desirable that the ink set of the present Embodiment B be used inan ink jet recording method which is a recording method in which liquiddroplets of ink are caused to jet from nozzles, and these liquiddroplets are caused to adhere to a recording medium, so that charactersand/or images are formed, and it is especially desirable that this inkset be used in an on-demand type ink jet recording method. Examples ofon-demand type ink jet recording methods include piezoelectric elementrecording methods in which recording is performed using piezoelectricelements that are disposed in a printer head, hot jet recording methodsin which recording is performed using thermal energy created by heaterssuch a heat-generating resistance elements or the like disposed in aprinter head, and other similar recording methods. The ink set of thepresent Embodiment B can be appropriately used in any of these ink jetrecording methods.

The present invention can provide a recording apparatus comprising theink set of the abovementioned Embodiment B without any particularrestrictions; preferably, this is a recording apparatus using the inkjet recording system described above.

Besides inks of the three primary colors of subtraction color mixing, i.e., yellow, magenta and cyan, the ink set of the present Embodiment Balso comprises a light magenta ink, a light cyan ink and two or moreblack inks with different pigment concentrations. Accordingly, the colorreproduction range is broad, the graininess caused by dot expression isfavorably [reduced], and metamerism can be reduced by using specifiedpigment types. Furthermore, both monochromatic and color images can bestably output with high image quality, and the output tends not to beaffected by conditions of the output environment such as temperature andthe like; as a result, a stable gray balance is obtained.

Ink jet printers are designed so that the same output can be obtainedany time at any place; however, since liquid inks are used, there is apossibility that the output may be affected by changes in the externalenvironment (such as temperature and the like) that cause a variation inthe viscosity of the inks. The reason for this is that in the case of anink jet printer that causes ink to jet from a head under pressure, thedischarge amount varies if the viscosity of the ink varies. In order toreduce this effect, the head driving comprises a function thatcompensates for the temperature at the time of output; in actuality,however, there is a possibility that the output will be subject tominute effects. Furthermore, besides temperature, the output is alsoaffected by the humidity, the recording medium used (ink jet medium) andthe like, which may cause minute color variations.

In the present Embodiment B, variation in the colors that are outputaccording to the environment can be suppressed by outputting as muchblack (a non-color) as possible, and outputting a light black in theimages.

Embodiments C and D

Here, the present Embodiments C and D will be described in the followingorder.

-   -   (1) Construction of the printing system using the ink sets of        Embodiments C and D    -   (2) Printing processing    -   (3) Printing of images    -   (4) Light source dependence (metamerism)    -   (5) Summary        (1) Construction of the Printing System Using the Ink Sets of        Embodiments C and D:

FIG. 4 shows the schematic hardware construction of a printing systemusing the inks sets of the present Embodiments C and D. Furthermore,FIG. 5 shows the schematic hardware construction of the printer, andFIG. 6 is a schematic structural diagram of the main control system ofthe printing apparatus realized by means of a computer. In the figures,the computer 10 comprises a CPU 11, and this CPU 11 can access a ROM 13and RAM 14 (in which the BIOS and the like are described) via a systembus 12.

Furthermore, a hard disk drive (HDD) 15, a flexible disk drive 16 and aCD-ROM drive 17 used as external memory devices are connected to thesystem bus 12, and an OS 20, application program (APL) 25 and the likestored in the HDD 15 are transferred to the RAM 14, so that the CPU 11executes software by appropriately accessing the ROM 13 and RAM 14.Specifically, various programs are executed using the RAM 14 as atemporary work area.

Operating input devices such as a keyboard 31, mouse 32 and the like areconnected to the computer 10 via a serial communications I/O 19 a, and adisplay 18 used for display purposes is also connected via a video boardnot shown in the figures. Furthermore, a connection with the printer 40is possible via a parallel communications I/O 19 b. Moreover, theconstruction of the present computer 10 is shown in simplified terms;however, a computer having a common construction (as a personalcomputer) can be used. Of course, the computer in which the presentEmbodiments C and D are used is not limited to a personal computer. Thisembodiment is a so-called desktop type computer; however, a notebooktype computer or a computer capable of mobile operation may also beused. Likewise the connection between the computer 10 and the printer 40is not necessarily limited to the connection described above. Varioustypes of connection functions such as a serial interface, an SCSI or USBconnection or the like may also be used, and the same is true regardingany type of connection configuration that may be developed in thefuture.

In this example, various types of programs are stored in the HDD 15;however, the storage medium is not limited to this. For example, aflexible disk 16 a or CD-ROM 17 a may also be used. The programsrecorded in these storage media are read into the computer 10 via theflexible disk drive 16 or CD-ROM drive 17, and are installed in the HDD15. Furthermore, the computer is controlled by reading these programsinto the RAM 14 via the HDD 15. Moreover, the recording medium is notlimited to this; an optical-magnetic disk or the like may also be used.In regard to semiconductor devices, nonvolatile memories such as flashcards or the like may also be used, and in cases where an external filesave is accessed and downloading is performed via a modem orcommunications circuit, the present Embodiments C and D are utilizedwith the communications circuit as a transfer medium.

Meanwhile, as is shown in FIG. 5, a CPU 41, ROM 42, RAM 43, ASIC 44,control IC 45, parallel communications I/O 46, interface (I/F) 47 (usedto transmit image data, driving signals and the like) and the like areconnected to a bus 40 a installed inside the printer 40. Furthermore,the CPU 41 controls various parts according to programs written into theROM 42 while utilizing the RAM 43 as a work area. The ASIC 44 is an ICthat is customized in order to drive a printing head not shown in thefigures; this ASIC 44 performs processing that is used to drive theprinting head while exchanging specified signals with the CPU 41.Furthermore, this part outputs printing voltage data to the head drivingpart 49.

The head driving part 49 is a circuit comprising a dedicated IC, drivingtransistors and the like. This same head driving part 49 produces aprinting voltage pattern in the piezoelectric elements contained in theprinting head on the basis of the printing voltage data that is inputfrom the ASIC 44. In regard to the ink sets of the present Embodiments Cand D, cartridge holders 48 that can mount ink cartridges 48 a through48 f filled with pigment type inks of six colors are connected to theprinting head via tubes for each ink, so that the printing head issupplied with the respective inks.

Furthermore, ink is discharged by the driving of piezoelectric elementsin ink compartments that communicate between the tubes and dischargeports. Furthermore, in the present embodiment, a construction in whichall-purpose CMYK inks and RV inks are used is employed. Moreover, theeffect of the present Embodiments C and D is more conspicuouslymanifested in the case of pigment type inks; however, dye type inks mayalso be used.

Six sets of nozzle rows that discharge the respective inks of six colorsare formed so that these nozzles are lined up in the main scan directionof the printing head on the ink discharge surface of the printing head.In each of the nozzle rows, a plurality of nozzles (e. g., 48 nozzles)are disposed at fixed intervals in the sub-scan direction.

The cartridge holders 48 comprise ink supply needles, and these inksupply needles form ink supply passages by contacting ink supply ports(not shown in the figures) formed in the ink cartridges 48 a through 48f, so that the inks inside the ink cartridges are supplied to theprinting head via tubes. The control IC 45 is an IC that is mounted inorder to control cartridge memories constituting nonvolatile memoriesthat are mount in the respective ink cartridges 48 a through 48 f. Theapparatus is devised so that when the ink cartridges are mounted in thecartridge holders 48, the cartridge memories are electrically connectedto the control IC 45. The CPU 41 exchanges specified signals with thecontrol IC 45, and performs the read-out of information concerningcolors and residual amounts of inks stored in the cartridge memories,alteration of information concerning the residual amounts of inks andthe like.

The parallel communications I/O 46 is connected with the parallelcommunications I/O 19 b of the computer 10, and the printer 40 receivesinformation that is transmitted from the computer 10, e. g., printingjobs comprising data designating CMYKRV dot formation densities, pagedescription language and the like, via the parallel communications I/O46. Furthermore, when various types of requests are received from thecomputer 10, the communications I/O outputs information indicating theink colors and mounting conditions from the control IC 45 to thecomputer 10. A carriage mechanism 47 a and paper feed mechanism 47 b areconnected to the I/F 47. The paper feed mechanism 47 b comprises a paperfeed motor, paper feed rollers and the like, and performs a sub-scan bysuccessively feeding a printing recording medium such as printing paperor the like. The carriage mechanism 47 a comprises a carriage on whichthe printing head is mounted, a carriage motor which causes thiscarriage to move via a timing belt and the like, and causes the printinghead to perform a main scan. In the printing head in which a pluralityof nozzles are disposed in the sub-scan direction, the piezoelectricelements are driven by driving signals output by the head driving part49 on the basis of head data comprising rows of bits, so that inkdroplets are discharged from the respective nozzles in dot units.

This printer 40 performs printing under the control of a printer driverinstalled in the computer 10. In the computer 10 of the presentembodiment, as is shown in FIG. 6, a printer driver (PRTDRV) 21, aninput device driver (DRV) 22 and a display driver (DRV) 23 are builtinto the OS 20. The display DRV 23 is a driver which controls thedisplay of image data and the like in the display 18, and the inputdevice DRV 22 is a driver which receives code signals from theabovementioned keyboard 31 or mouse 32 that are input via the serialcommunications I/O 19 a, and thus receives various input operations. TheAPL 25 is an application program that allows the execution of colorimage retouching and the like; the user can cause these color images tobe printed by the printer 40 by operating the abovementioned operatinginput devices while this APL 25 is executed. Specifically, the APL 25reads out the image data 15 a recorded in the HDD 15 according to theinstructions of the user to the RAM 14, and causes images based on thisimage data 15 a to be displayed on the display 18 via the display DRV23. When the user operates the abovementioned input devices, the contentof the operations is acquired via the input device DRV 22, and thiscontent is interpreted; the APL 25 performs various types of processingsuch as printing instructions, retouching and the like in accordancewith this operation content.

When printing instructions are issued by the APL 25, the abovementionedPRTDRV 21 is driven, and the PRTDRV 21 feeds out data to the display DRV23, so that UI (not shown in the figures) used to input informationrequired for printing is displayed. Using this UI (not shown in thefigures), the user can set various parameters such as the number ofprinting parts, number of pages and the like, and the PRTDRV 21 receivesthese parameters via the input device DRV 22. When the PRTDRV 21receives these parameters, printing data is prepared while theabovementioned image data 15 a designating colors by sRGB iscolor-converted into respective CMYKRV color data with reference to anLUT 15 b (described later), and printing is performed by sending outthis printing data to the abovementioned printer 40.

(2) Printing Processing:

In the present embodiment, the abovementioned PRTDRV 21 causes theprinter 40 to perform printing while performing a color conversion usingthe LUT 15 b. In order to perform printing, this PRTDRV 21 comprises theimage data acquisition module 21 a, color conversion module 21 b,halftone processing module 21 c and printing data production module 21 dshown in FIG. 6. When the user gives instructions for printing to beexecuted by the PRTDRV 21 using the abovementioned APL 25, printingprocessing is executed according to the flow chart shown in FIG. 7. Whenprinting processing is initiated, the abovementioned image dataacquisition module 21 a acquires the image data 15 a stored in theabovementioned RAM 14 in step S100.

Then, the image data acquisition module 21 a starts the abovementionedcolor conversion module 21 b in step S105. The color conversion module21 b is a module that converts RGB halftone values into CMYKRV halftonevalues; this color conversion module 21 b converts the respective dotdata of the abovementioned image data 15 a into CMYKRV dot data in thesame step S105. When CMYKRV halftone data is produced as a result ofsuch a color conversion being performed by the color conversion module21 b, the abovementioned halftone processing module 21 c is started bythe same color conversion module 21 b in step S110, and the CMYKRVhalftone data is transferred to the abovementioned halftone processingmodule 21 c.

The halftone processing module 21 c is a module which performs halftoneprocessing that is used to convert the CMYKRV halftone values of therespective dots and express these values as the recording density of inkdroplets; in the same step S110, this halftone processing module 21 cproduces head driving data that is used to cause ink to adhere [to therecording medium] at the recording density obtained followingconversion. The printing data production module 21 d receives this headdriving data, and rearranges the data into the order used by the printer40 in step S115. Specifically, a discharge nozzle array (not shown inthe figures) used as an ink discharge device is mounted in the printer40, and a plurality of nozzles are lined up in the sub-scan direction inthis nozzle array; accordingly, data separated into a number of dots inthe sub-scan direction is simultaneously used.

Then, the printing data production module 21 d performs a rasterizationthat rearranges the order so that the data that is to be simultaneouslyused (among the data that is lined up in the main scan direction) issimultaneously buffered by the printer 40. Following this rasterization,printing data is produced by adding specified information such as theimage resolution and the like, and the printing data production module21 d outputs this data to the printer 40 via the abovementioned parallelcommunications I/O 19 b in step S120. In the printer 40, the imagesdisplayed on the abovementioned display 18 are printed on the basis ofthis printing data. In this printer 40, inks of respective CMYKRV colorsare caused to adhere to the printing medium on the basis of CMYKRVhalftone data as described above. The abovementioned processing isexecuted for all rasters (step S125).

Here, the abovementioned LUT 15 b is a table in which sRGB data andCMYKRV data are caused to correspond; in step S105, a correspondence isestablished between arbitrary RGB halftone values and CMYKRV halftonevalues by performing interpolation calculations on the basis of thesereference points; here, various universally known techniques may be usedas the method of interpolation calculations. For example, linearinterpolation calculations, spline interpolation calculations or thelike may be used. Furthermore, the system may also be constructed sothat the reference points provided in the LUT 15 b are developed into alarger number of reference points by interpolation calculations, and sothat the developed reference points are buffered in the RAM 14, andfurther interpolation calculations are performed with reference to thereference points inside this RAM 14. Of course, besides a constructionin which color conversion is performed using a color conversion table,it would also be possible to perform color conversion using a profile orthe like in which a color conversion matrix is defined beforehand.

(3) Printing of Images:

Next, the operation that is performed when images are printed in theabovementioned construction will be described with reference to theoperating schematic diagram shown in FIG. 8. In this figure, the displayscreen of the display 18 shows the abovementioned APL 25 executionscreen; when image data 15 a is read out by the APL 25, this image data15 a is stored in the RAM 14, and an image A is displayed on the display18 on the basis of the image data 15 a by the processing of the displayDRV 23. Since the effect of the present Embodiments C and D isespecially conspicuous in the case of low-saturation substantiallycolorless images, an image A which has a dark background and containsconsiderable substantially colorless areas will be described as anexample. In the APL 25, various types of retouching and the like can beperformed on the image A displayed on the display 18, and printingexecution instructions for this image A can be issued. The executionscreen in the same figures is a screen in a state in which printingexecution instructions are issued by reading out image data 15 a storedin the HDD 15; printing execution instructions can be issued byselecting the printing tab in the file menu by operating the mouse 32.

Ideally, in the substantially colorless areas contained in the image A,the spectroscopic reflectance for all wavelengths of visible light issubstantially constant; however, variations in coloring that occur insubstantially colorless areas are easily recognized by the human eye,and if wavelength regions in which the spectroscopic reflectance is notconstant are present, variations in the energy of the reflected lightbecome more prominent when the light source varies so that energy atspecified wavelengths becomes stronger, thus resulting in a tinge of aspecified color (so-called metamerism). However, if the combination ofthe spectroscopic reflectance values of the CMY inks is appropriatelyadjusted, the spectroscopic reflectance of substantially colorless areascan be made constant over all wavelengths of visible light, i. e., canbe caused to approach a substantially flat value, so that the systembecomes less susceptible to the effects of variations in the lightsource.

In the present embodiment, sRGB data is converted into CMYKRV data bythe LUT15 b, and ink cartridges 48 a through 48 f filled with CMYKRVinks are mounted in the printer 40. Furthermore, by mounting an M ink(described later) having a spectroscopic reflectance of a specifiednature with respect to variations in the spectroscopic reflectancevalues of the C and Y inks in the [M] ink cartridge, an effect isobtained which is such that regardless of whether the image B obtainedby printing in the printer 40 is viewed under the light source C (indoorlighting) or light source D (sunlight), there is little variation incolor according to the light source, and no color tinge is generated inthe substantially colorless areas.

(4) Reduction of Light Source Dependence (Metamerism):

Below, the device whereby the light source dependence of color isreduced using such a construction in the present embodiment will bedescribed. First, the manner in which colors are viewed by the human eyewill be described. FIG. 9 is an explanatory diagram illustrating themanner in which colors are viewed in the human eye. Since the human eyedistinguishes differences in color according to the wavelength of light,the manner of viewing colors can be regulated by regulating how thehuman eye reacts to certain wavelengths of light.

The wavelengths of light that are incident on the human eye from printedmatter are regulated by the distribution of wavelengths contained in thelight source, i. e., the spectroscopic distribution L(λ) of the lightsource, and the distribution of wavelengths contained in the reflectedlight that is reflected from the printed matter, i. e., thespectroscopic reflectance R(λ) of the printed matter. The reaction ofthe human eye to wavelengths of light is regulated by the isochromaticfunctions x(λ), y(λ), z(λ). Here, x(λ) indicates the sensitivity to thered component, y(λ) indicates the sensitivity to the green component,and z(λ) indicates the sensitivity to the blue component. Furthermore,the respective isochromatic functions are ordinarily indicated as x barand the like by adding a “horizontal line” above the letter of thefunction; in the present specification, however, the “horizontal line”is omitted for the sake of simplicity. Furthermore, in an ink jetprinter such as the printer 40 in the present embodiment, thespectroscopic reflectance R(λ) is produced by superimposing thespectroscopic reflectance of the printing paper in the portions wherethe printing paper is exposed and the spectroscopic reflectance of theink (linear coupling with the area ratio as a coefficient).

In these formulae, the abovementioned λ is the wavelength of the light.

The manner of viewing colors is calculated as three stimulus values XYZis calculated by multiplying the abovementioned spectroscopicdistribution L(λ) of the light source, spectroscopic reflectance R(λ)and isochromatic functions x(λ), y(λ) and z(λ), and integrating thisproduct by the wavelength. Specifically, the three stimulus values XYZare calculated by the following Equation (1).X=∫L(λ)R(λ)x(λ)dλY=∫L(λ)R(λ)y(λ)dλ  (1)Z=∫L(λ)R(λ)z(λ)dλ

The manner in which colors are viewed by the human eye is regulated bythese three stimulus values XYZ. Specifically, colors are definitivelydetermined by combinations of the three stimulus values XYZ. Among thefactors that determine these three stimulus values, the abovementionedisochromatic functions x(λ), y(λ) and z(λ) are mean values ofcharacteristics of the human eye, and cannot be artificially varied,while the abovementioned spectroscopic distribution L(λ) of the lightsource naturally fluctuates according to variations in the light source.The present Embodiments C and D that reduce light source dependence areembodiments that take countermeasures when this spectroscopicdistribution L(λ) of the light source fluctuates. Among the factors thatdetermine the three stimulus values, the major portion of theabovementioned spectroscopic reflectance R(λ) depends on thespectroscopic reflectance of the inks; accordingly, this spectroscopicreflectance can be artificially varied by varying the amounts of theinks and the number of colors of inks. Therefore, the presentembodiments C and D employ an M ink which has specified properties withrespect to the spectroscopic reflectance characteristics of the C and Yinks in order to convert this spectroscopic reflectance R(λ) into adesirable distribution.

The device used to reduce the light source dependence by employing suchan M ink will be described below. Colorless areas in which the effect ofthe present Embodiments C and D is most conspicuously manifested will bedescribed as an example. FIG. 10 shows the spectroscopic reflectancevalues of the CMY inks used in the present embodiment (C ink: curveconnected by O, M ink: curve connected by solid triangles, Y ink: curveconnected by Δ, and the spectroscopic reflectance values of thecolorless gray (curve connected by solid diamonds) formed by mixingthese CMY inks. In the same figures, the vertical axis indicates thespectroscopic reflectance (%), and the horizontal axis indicates thewavelength (nm). The spectroscopic reflectance values of these C and Yinks have characteristics similar to those in a conventional printer. Asis shown in the same figure, the spectroscopic reflectance of the C inkrises with an increase in wavelength from a wavelength of 400 nm, trendsat approximately 85% at wavelengths of approximately 450 nm to 500 nm,drops with an increase in wavelength from approximately 500 nm to 600nm, and trends between 20% and 30% at wavelengths of 600 nm to 700 nm.

The spectroscopic reflectance of the Y ink rises abruptly with anincrease in wavelength from a wavelength of approximately 450 nm, andtrends at approximately 85% at wavelengths of 500 nm to 700 nm. Here,the spectroscopic reflectance of the C ink and the spectroscopicreflectance of the Y ink cross at a wavelength that is biased toward 500nm from the intermediate point between 500 nm and 550 nm. Furthermore,the spectroscopic reflectance of the M ink first rises with an increasein the wavelength from a wavelength of 400 nm, then reaches a maximumand drops between wavelengths of 400 nm and 450 nm, and forms a curvewith a downward protruding shape between wavelengths of 450 nm and 550nm. This spectroscopic reflectance then rises with an increase inwavelength from wavelengths beyond 550 nm, and trends at approximately80% at wavelengths of 600 nm or greater. In cases where a substantiallycolorless area is formed by these CMY inks, all of these CMY inks aredischarged onto the printing paper.

Here, the characterizing features of the shape of the spectroscopicreflectance of the M ink in the present embodiments described above willbe described.

Characterizing Features of Embodiment C:

(1) The embodiment has characteristics which are such that thespectroscopic reflectance is 0.4 or less at least at the wavelengthwhere the spectroscopic reflectance of the Y ink and the spectroscopicreflectance of the C ink intersect.

(2) The embodiment has characteristics which are such that a wavelengthregion in which the spectroscopic reflectance is 0.4 or less is formedin at least the range extending from the wavelength where thespectroscopic reflectance values of the C and Y inks intersect to awavelength of 550 nm.

Characterizing Features of Embodiment D:

(1) The embodiment has characteristics which are such that at thewavelength where the spectroscopic reflectance values of the C and Yinks intersect, the spectroscopic reflectance values of the C and Y inksat the same wavelength are 0.4 or less.

(2) The embodiment has characteristics which are such that a wavelengthregion in which the spectroscopic reflectance is 0.4 or less relative tothe spectroscopic reflectance value of the Y ink is formed in at leastthe range extending from the wavelength where the spectroscopicreflectance values of the C and Y inks intersect to a wavelength of 550nm.

“Gray” in FIG. 10 indicates the superimposed spectroscopic reflectanceR(λ) in a case where all of the CMY inks that form such spectroscopicreflectance curves are discharged onto the printing paper. Thiscolorless spectroscopic reflectance R(λ) is ideally constant over allwavelengths, i. e., is ideal as the gray in FIG. 10 approaches astraight line that is parallel to the horizontal axis. In the presentembodiment, irregularities in the colorless spectroscopic reflectanceR(λ) can be reduced by using an M ink that has the spectroscopicreflectance described above, so that this spectroscopic reflectance R(λ)can be caused to approach more closely to a substantially flat curve.

Here, examples of the ink compositions of the CMYKRV inks used in thepresent embodiments (applicable to both Embodiments C and D) are shownin FIG. 11. In the same figure, the C ink uses “C. I. pigment blue 15:3”as a coloring material, and has a construction comprising 0.5 wt %styrene-acrylic acid copolymer, 15 wt % glycerol, 5 wt % ethyleneglycol, 2 wt % 2-pyrrolidone, 5 wt % 1,2-hexanediol, and 0.5 wt % OlfinE1010. The balance in wt % is ion exchange water. The amount of coloringmaterial is 1.5 wt %. The Y ink uses “C. I. pigment yellow 74” as acoloring material, and has a construction comprising 1 wt %styrene-acrylic acid copolymer, 15 wt % glycerol, 5 wt % ethyleneglycol, 2 wt % 2-pyrrolidone, 5 wt % 1,2-hexanediol, and 0.5 wt % OlfinE1010. The balance in wt % is ion exchange water. The amount of coloringmaterial is 3 wt %.

The K ink uses “C. I. pigment black 7” as a coloring material, and has aconstruction comprising 1.5 wt % styrene-acrylic acid copolymer, 15 wt %glycerol, 5 wt % ethylene glycol, 2 wt % 2-pyrrolidone, 5 wt %1,2-hexanediol, and 0.5 wt % Olfin E1010. The balance in wt % is ionexchange water. The amount of coloring material is 1.5 wt %. The R inkuses “C. I. pigment red 178” as a coloring material, and has aconstruction comprising 0.7 wt % styrene-acrylic acid copolymer, 15 wt %glycerol, 5 wt % ethylene glycol, 2 wt % 2-pyrrolidone, 5 wt %1,2-hexanediol, and 0.5 wt % Olfin E1010. The balance in wt % is ionexchange water. The amount of coloring material is 2 wt %.

The V ink uses “C. I. pigment violet 23” as a coloring material, and hasa construction comprising 0.7 wt % styrene-acrylic acid copolymer, 15 wt% glycerol, 5 wt % ethylene glycol, 2 wt % 2-pyrrolidone, 5 wt %1,2-hexanediol, and 0.5 wt % Olfin E1010. The balance in wt % is ionexchange water. The amount of coloring material is 2 wt %. Furthermore,the M ink used in the present embodiment uses “C. I. pigment violet 19”as a coloring material, and has a construction comprising 0.7 wt %styrene-acrylic acid copolymer, 15 wt % glycerol, 5 wt % ethyleneglycol, 2 wt % 2-pyrrolidone, 5 wt % 1,2-hexanediol, and 0.5 wt % OlfinE1010. The balance in wt % is ion exchange water.

The amount of coloring material in the M ink is 2 wt %. Conventionally,on the other hand, an M ink has been employed in which the coloringmaterial is “C. I. pigment red 202”, and the ink has a constructioncomprising 0.5 wt % styrene-acrylic acid copolymer, 15 wt % glycerol, 5wt % ethylene glycol, 2 wt % 2-pyrrolidone, 5 wt % 1,2-hexanediol, and0.5 wt % Olfin E1010, with the balance in wt % being ion exchange waterand the amount of coloring material being set at 1.5 wt %.

Other desirable M ink compositions that can be used in the presentembodiments are shown below.

(1) A composition containing one or more high-boiling-point compoundsselected from among polyhydric alcohol type compounds and saccharides atthe rate of 5% or greater.

(2) A composition containing one or more polar solvents selected fromamong glycol ether type compounds and alkyldiol type compounds at therate of 1% or greater.

(3) A composition containing one or more surfactants selected from amongacetylene glycol type compounds and acetylene alcohol type compounds atthe rate of 0.1% or greater.

(4) A composition containing one or more high-boiling-point compoundsselected from among polyhydric alcohol type compounds and saccharides atthe rate of 5% or greater, one or more polar solvents selected fromamong glycol ether type compounds and alkyldiol type compounds at therate of 1% or greater, and one or more surfactants selected from amongacetylene glycol type compounds and acetylene alcohol type compounds atthe rate of 0.1% or greater.

(5) A composition containing a resin at the rate of 0.1% or greater.

Here, the color reproduction regions of the ink sets of the presentEmbodiments C and D are shown in FIGS. 12 and 13.

In the figures, the upward direction is the Y direction, the leftwarddirection is the G direction, and the rightward direction is the Rdirection. Furthermore, the color reproduction region indicated by thedotted line is the color reproduction region of a conventional ink setof CMY inks, and the color reproduction region indicated by the one-dotchain line is the color reproduction region of an ink set of CMY inksusing a Y ink that has an effect in reducing metamerism. Moreover, thecolor reproduction region indicated by the solid line is the colorreproduction region of the ink sets of CMY inks in the presentEmbodiments C and D. Thus, in the case of the ink set of CMY inks usinga Y ink that has an effect in reducing metamerism, the colorreproduction region in the G direction is conspicuously narrowed (it canbe seen that although the region is broadened with respect to the Ydirection, the region as a whole is narrow).

On the other hand, in the case of the ink sets of CMY inks in thepresent Embodiments C and D, the color reproduction region is broad inthe G and Y directions and in the R direction, as in the conventionalink set of CMY inks.

Accordingly, it can be seen that the color reproduction region isbroadened on the whole compared to the color reproduction region of theabovementioned ink set of CMY inks using a Y ink that has an effect inreducing metamerism. Moreover, the color reproduction region in the Rdirection is broader than that in the conventional ink set of CMY inks.Specifically, the ink set of CMY inks provided by the present inventioncan broaden the color reproduction region compared to that of aconventional ink set of CMY inks, in addition to reducing metamerism. Inthis case, it is seen that the color reproduction region in the GYdirection is especially broadened at a high lightness such as L*=70. Gat this lightness is an important color for reproducing the colors ofgrass and new foliage; the ink sets of the present Embodiments C and Dare also very superior in terms of allowing the accurate reproduction ofthis important color in particular. Thus, particularly as a result ofusing an M ink formed by a novel composition, the ink sets of CMY inksin the present Embodiments C and D can reduce the light sourcedependence of substantially colorless areas, and also make it possibleto obtain the effect of allowing an expansion of the color reproductionregion.

Here, in the present embodiments, in cases where a printer 40 with adetachable ink set is used, there may be cases in which printing isperformed with the abovementioned ink set having a conventionalreproduction region mounted, and cases in which printing is performedwith the ink set having the color reproduction region of the presentinvention mounted. In such cases, it is desirable that it be possible toalter the LUT 15 b used in the color conversion processing performed bythe color conversion module 21 b in accordance with the colorreproduction region of the ink set mounted in the printer 40.

Accordingly, an LUT which is desirable for use in color conversion incases where a conventional ink set is mounted in the printer 40, and anLUT which is desirable for use in cases where the ink set of the presentEmbodiment C or D is mounted in the printer 40, are prepared as LUTs 15b.

Furthermore, in such cases, it is advisable to devise the system so thatan ID that indicates the type of the ink set (type allowing differencesin the color reproduction region to be distinguished) is incorporatedinto the status that can be transmitted and received by two-waycommunications between the printer 40 and the PRTDRV 21, and so that thePRTDRV 21 acquires this status from the side of the printer 40 at thetime of printing, and alters the LUT 15 b used in color conversion.Here, a schematic flow chart of the color conversion processing that isperformed by the color conversion module 21 b in a case where thismethod is used is shown in FIG. 14.

In the same figure, the status is acquired by two-way communicationswith the printer 40, and the ID of the ink set stored in the printer 40is acquired (step S205). Then, on the basis of this ID, the optimal LUTis selected (step S210), and a color conversion from sRGB data to CMYKRVdata is performed using this selected LUT (step S215). As result, colorconversion processing suited to the color reproduction characteristicsof the ink set can be performed. In the abovementioned embodiment, aconstruction was described in which the LUT used in color conversionprocessing was switched on the basis of two ink sets. However, thepresent invention is of course not limited to such a construction; itgoes without saying that it would also be possible to devise the systemso that the LUT used for appropriate color conversion is switched basedon the ID for two or more ink sets.

(5) Summary:

Thus, by constructing the spectroscopic reflectance characteristics ofthe M ink so that the spectroscopic reflectance of this ink is 0.4 orless at least at the wavelength at which the spectroscopic reflectanceof the Y ink and the spectroscopic reflectance of the C ink intersect(Embodiment C), or by constructing these characteristics so that thespectroscopic reflectance of this ink is 0.4 or less relative to thespectroscopic reflectance values of the Y ink and C ink at least at thewavelength at which the spectroscopic distributions of the Y ink and Cink intersect (Embodiment D), it is possible to make the grayspectroscopic reflectance characteristics substantially flat throughoutthe entire visible wavelength region, so that the light sourcedependence (metamerism) of this gray can be reduced.

Embodiment E

The present invention can also provide an ink set in which both halftoneproperties of the recorded images and a suppression of graininess areachieved, e. g., an ink set comprising a yellow ink (Y), magenta ink(M), light magenta ink (Lm), cyan ink (C), light cyan ink (Lc), twotypes of black inks (K) (high-concentration black inks) and two types oflight black inks (Lk) (medium-concentration black ink andlow-concentration black ink)(this invention is referred to as EmbodimentE hereinbelow).

A concrete example of the ink set of the present Embodiment E is asfollows:

-Y ink: C.I. pigment yellow 74 5.0 wt % Dispersing agent (styrene -acrylic acid copolymer) 1.5 wt % Glycerol 16.0 wt % 1,2-Hexanediol 5.0wt % Triethanolamine 0.9 wt % BYK348 0.5 wt % Ion exchange water balancetotal 100.0 wt % -M ink: C.I. pigment violet 19 6.0 wt % Dispersingagent (styrene - acrylic acid copolymer) 1.8 wt % Glycerol 10.0 wt %1,2-Hexanediol 5.0 wt % Triethanolamine 0.9 wt % BYK348 0.5 wt % Ionexchange water balance total 100.0 wt % -Lm ink: C.I. pigment violet 191.0 wt % Dispersing agent (styrene - acrylic acid copolymer) 0.3 wt %Glycerol 26.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.9 wt %BYK348 0.5 wt % Ion exchange water balance total 100.0 wt % -C ink: C.I.pigment blue 15:3 4.0 wt % Dispersing agent (styrene - acrylic acidcopolymer) 1.2 wt % Glycerol 11.0 wt % 1,2-Hexanediol 5.0 wt %Triethanolamine 0.9 wt % BYK348 0.5 wt % Ion exchange water balancetotal 100.0 wt % -Lc ink: C.I. pigment blue 15:3 1.0 wt % Dispersingagent (styrene - acrylic acid copolymer) 0.3 wt % Glycerol 24.0 wt %1,2-Hexanediol 5.0 wt % Triethanolamine 0.9 wt % BYK348 0.5 wt % Ionexchange water balance total 100.0 wt % -K ink (MK: matte black ink):Carbon black 6.0 wt % Glycerol 12.0 wt % 1,2-Hexanediol 5.0 wt %Triethanolamine 0.9 wt % BYK348 1.0 wt % Ion exchange water balancetotal 100.0 wt % -K ink (PK: photo black ink): Carbon black 1.5 wt %Dispersing agent (styrene - acrylic acid copolymer) 1.5 wt % Glycerol20.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.9 wt % BYK348 0.5 wt% Ion exchange water balance total 100.0 wt % -Lk ink(medium-concentration black ink): Carbon black 0.76 wt % Dispersingagent (styrene - acrylic acid copolymer) 0.76 wt % Glycerol 22.0 wt %1,2-Hexanediol 5.0 wt % Triethanolamine 0.9 wt % BYK348 0.5 wt % Ionexchange water balance total 100.0 wt % -Lk ink (low-concentration blackink): Carbon black 0.24 wt % Dispersing agent (styrene - acrylic acidcopolymer) 0.24 wt % Glycerol 22.0 wt % 1,2-Hexanediol 5.0 wt %Triethanolamine 0.9 wt % BYK348 0.5 wt % Ion exchange water balancetotal 100.0 wt %

Such an ink set of Embodiment E can improve the halftone properties andeffect in suppressing graininess even further than an ink set thatcomprises special color inks such as a red ink, violet ink or the likein addition to YMC inks.

In the ink set of the present Embodiment E, C. I. pigment violet 19 isdesirable for use as the coloring material of the magenta ink in thatthe use of such a coloring material not only makes it possible torealize a high saturation and a superior graininess suppressing effectin high a* regions, but also to suppress metamerism.

Furthermore, in the ink set of the present Embodiment E, it is desirablethat the ink set contain inks with a low coloring material concentration(light inks). Relative to the amounts of coloring material in the darkinks, the amounts of coloring material in these light inks (weightstandard) are preferably 0.12 to 0.3, and are even more preferably 0.16to 0.26. By using such proportions, it is possible to perform recordingwithout sacrificing the graininess suppressing effect at intermediatelightness values (in the vicinity of L* 60 to 70) even if the coloringmaterial concentration in the light inks is set at 3 wt % to 8 wt %.

Furthermore, in cases where both a graininess suppressing effect and ametamerism suppressing effect are obtained by controlling the lightnessin high-saturation portions, it is desirable to simultaneously use alight black ink which has a coloring material concentration (pigmentsolid content) of less than 1.5 wt %, and which has substantially nospectroscopic reflectance peaks, as in the abovementioned example in thepresent Embodiment E. It is desirable that the coloring materialconcentration in this light black ink be 1 wt % or less. Furthermore, itis even more desirable to use two types of inks, i. e., amedium-concentration black ink with a coloring material concentration of0.5 wt % or greater but less than 1.0 wt %, and a low-concentrationblack ink with a coloring material concentration of less than 0.5 wt %,as light black inks.

Modified Embodiments

The present invention preferably provides the respective embodimentsdescribed above. However, the present invention is not limited to theseembodiments; various modifications are possible within limits thatinvolve no departure from the spirit of the present invention.

EXAMPLES

The present invention will be concretely described below in terms ofexamples of the present invention and comparative examples. However, thepresent invention is not limited in any way by these examples.

Example A

(Preparation of Ink Sets)

Yellow inks (Y1) and (Y2), magenta inks (M1) and (M2), a cyan ink (C1),light magenta inks (Lm1) and (Lm2), a light cyan ink (Lc1), an ink A(A1) and an ink B (B1) provided in the respective ink sets of theexamples and comparative examples shown in Table 1 were respectivelyprepared by ordinary methods. Specifically, the coloring materialcomponents were dispersed together with the dispersing agent components,and inks were then prepared by adding and mixing the other components,and filtering out insoluble components exceeding a fixed size. Therespective inks thus obtained were combined to form the ink sets of therespective examples and comparative examples.

<Yellow ink (Y1)> C.I. pigment yellow 74 5.0 wt % Dispersing agent(styrene - acrylic acid copolymer) 1.5 wt % Glycerol 15.0 wt %1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt % Olfin E1010 0.5 wt %Ion exchange water balance total 100.0 wt % <Yellow ink (Y2)> C.I.pigment yellow 74 3.0 wt % Dispersing agent (styrene - acrylic acidcopolymer) 0.9 wt % Glycerol 15.0 wt % 1,2-Hexanediol 5.0 wt %Triethanolamine 0.5 wt % Olfin E1010 0.5 wt % Ion exchange water balancetotal 100.0 wt % <Magenta ink (M1)> C.I. pigment violet 19 6.0 wt %Dispersing agent (styrene - acrylic acid copolymer) 1.8 wt % Glycerol15.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt % Olfin E10100.5 wt % Ion exchange water balance total 100.0 wt % <Magenta ink (M2)>C.I. pigment red 202 6.0 wt % Dispersing agent (styrene - acrylic acidcopolymer) 1.8 wt % Glycerol 15.0 wt % 1,2-Hexanediol 5.0 wt %Triethanolamine 0.5 wt % Olfin E1010 0.5 wt % Ion exchange water balancetotal 100.0 wt % <Cyan ink (C1)> C.I. pigment blue 15:3 4.0 wt %Dispersing agent (styrene - acrylic acid copolymer) 1.2 wt % Glycerol15.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt % Olfin E10100.5 wt % Ion exchange water balance total 100.0 wt % <Light magenta ink(Lm1)> C.I. pigment violet 19 2.0 wt % Dispersing agent (styrene -acrylic acid copolymer) 0.6 wt % Glycerol 15.0 wt % 1,2-Hexanediol 5.0wt % Triethanolamine 0.5 wt % Olfin E1010 0.5 wt % Ion exchange waterbalance total 100.0 wt % <Light magenta ink (Lm2)> C.I. pigment red 2022.0 wt % Dispersing agent (styrene - acrylic acid copolymer) 0.6 wt %Glycerol 15.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt %Olfin E1010 0.5 wt % Ion exchange water balance total 100.0 wt % <Lightcyan ink (Lc1)> C.I. pigment blue 15:3 1.5 wt % Dispersing agent(styrene - acrylic acid copolymer) 0.5 wt % Glycerol 15.0 wt %1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt % Olfin E1010 0.5 wt %Ion exchange water balance total 100.0 wt % <Ink A (A1)> C.I. pigmentred 177 2.5 wt % Dispersing agent (styrene - acrylic acid copolymer) 0.6wt % Glycerol 15.0 wt % 1,2-Hexanediol 5.0 wt % Triethanolamine 0.5 wt %Olfin E1010 0.5 wt % Ion exchange water balance total 100.0 wt % <Ink B(B1)> C.I. pigment violet 23 2.0 wt % Dispersing agent (styrene -acrylic acid copolymer) 0.6 wt % Glycerol 15.0 wt % 1,2-Hexanediol 5.0wt % Triethanolamine 0.5 wt % Olfin E1010 0.5 wt % Ion exchange waterbalance total 100.0 wt %

The inks used in the ink sets of the examples and comparative examples,and the types and contents (wt %) of the pigments used in the respectiveinks are shown in Table 1.

TABLE 1 Ink sets used. Y M C Lm Lc R V Example (1) Y1 M1 C1 — — — —Example (2) Y1 M1 C1 Lm1 Lc1 — — Example (3) Y2 M1 C1 Lm1 Lc1 A1 B1Comparative Example (1) Y1 M2 C1 — — — — Comparative Example (2) Y1 M2C1 Lm2 Lc1 — — Comparative Example (3) Y2 M2 C1 Lm2 Lc1 A1 B1 Pigmenttypes and amounts Y M C Lm Lc R V Example (1) PY74-5% PV19-6% PB15:3-4%— — — — Example (2) PY74-5% PV19-6% PB15:3-4% PV19-2% PB15:3-1.5% — —Example (3) PY74-3% PV19-6% PB15:3-4% PV19-2% PB15:3-1.5% PR177-2.5%PV23-2% Comparative Example (1) PY74-5% PR202-6% PB15:3-4% — — — —Comparative Example (2) PY74-5% PR202-6% PB15:3-4% PR202-2% PB15:3-1.5%— — Comparative Example (3) PY74-3% PR202-6% PB15:3-4% PR202-2%PB15:3-1.5% PR177-2.5% PV23-2%(Measurement of L* Values of Aqueous Solutions of Inks Diluted 1000Times by Weight)

The L* values (as stipulated by the Lab display system of the CIE) ofaqueous solutions (diluted 1000 times by weight) of the respective colorinks used in the respective ink sets of the examples and comparativeexamples were measured as follows using a U3300 manufactured by HitachiSeisakusho.

Specifically, two quartz cells with dimensions of 1 cm (length)×1 cm(width)×4 cm (height) and a volume of 4 mL were prepared, and thesecells were respectively used as a sample side cell and a reference sidecell. Pure water was added to both cells, and a base line was measuredand set. The reference side cell was left as is, and the pure water inthe sample side cell was replaced with an aqueous solution of the sampleink diluted 1000 times by weight. The aqueous solution of ink diluted1000 times by weight was prepared by transferring 1.00 g of each ink ineach ink set of the examples and comparative examples to a 1-L beaker,and further adding pure water to produce a total of 1000.00 g ofsolution.

Then, the sample side cell and reference side cell were set in themeasurement part, and the ultraviolet-visible transmission spectrum wasmeasured in the range of 380 to 800 nm at a photomultiplier voltage of200 V with the light source lamp set as a D2 lamp and WI lamp switchedat 340 nm, the lamp slit width set at 2.0 mm, the scanning speed of themeasurement interval set at 600 nm/min, and the transmissivity set at0.0 to 100.0% T. The L* values of aqueous solutions of the respectiveinks diluted 1000 times by weight calculated in this way are shownbelow. Furthermore, the a* values and b* values were similarlycalculated for the inks (A) and (B), and these values are also shownbelow.

-   -   L* values (Y1): 88, (M1): 63, (C1): 65, (Lm1): 81, (Lc1): 80,        (Y2): 91, (A1): 68, (B1): 49, (M2): 58, (Lm2): 80.    -   a* values (A1): 52, (B1): 67.    -   b* values (A1): −2, (B1): −66.

The pigment contents are determined in accordance with the selectedpigment types by thus setting the L* values in the CIE-stipulated Labdisplay system of aqueous solutions of the inks diluted 1000 times byweight.

(Abovementioned Y Values and Z Values in the Magenta and Light MagentaInks)

Dilute aqueous solutions with a pigment solid concentration of 0.01 wt %or less were prepared by dilution with pure water so that the Y value(in the XYZ display system stipulated by the CIE, as calculated from theultraviolet-visible transmission spectrum) of the magenta inks used inthe respective ink sets of the examples and comparative examples was 55.

In actuality, dilute solutions with pigment contents of 0.0010 wt %,0.0015 wt %, 0.0020 wt %, 0.0025 wt % and 0.0030 wt % were prepared. Todescribe the preparation method used in the case of Lm1 in concreteterms, 0.5 g, 0.75 g, 1.00 g, 1.25 g and 1.50 g samples of Lm1 wererespectively placed in 1-liter beakers, and samples were prepared byimmediately adjusting the amount to 1000.00 g. Samples were alsosimilarly prepared in the case of Lm2. Furthermore, to describe thepreparation method used in the case of M1 in concrete terms, 0.167 g,0.250 g, 0.333 g, 0.417 g and 0.500 g samples of M1 were respectivelyplaced in 1-liter beakers, and samples were prepared by immediatelyadjusting the amount to 1000.00 g. Samples were also similarly preparedin the case of M2.

These respective aqueous solutions were measured as follows using aU3300 manufactured by Hitachi Seisakusho. Specifically, two quartz cellswith dimensions of 1 cm (length)×1 cm (width)×4 cm (height) and a volumeof 4 mL were prepared, and these cells were respectively used as asample side cell and a reference side cell. Pure water was added to bothcells, these cells were set in the measurement part, and a base line wasmeasured and set. In regard to the measurement conditions, theultraviolet-visible transmission spectrum was measured in the range of380 to 800 nm at a photomultiplier voltage of 200 V with the lightsource lamp set as a D2 lamp and WI lamp switched at 340 nm, the lampslit width set at 2 mm, the scanning speed of the measurement intervalset at 600 nm/min, and the transmissivity set at 0.0 to 100.0% T.

Next, the reference side cell was left as is, and the pure water in thesample side cell was replaced with the respective aqueous solutions. Theultraviolet-visible transmission spectra were respectively measured, andthe Y and Z values in the XYZ display system stipulated by the CIE weremeasured on the basis of a D65 light source and a visual field angle of2 degrees.

These values were plotted in a graph with the Y value on the horizontalaxis and the Z value on the vertical axis, and were connected by curves,thus producing curve Lm1, curve Lm2, curve M1 and curve M2. Therespective Z values in the case of a Y value of 55 were determined fromthese curves, and are shown below.

(M1) Z value: 77 (Lm1) Z value: 77 (M2) Z value: 84 (Lm2) Z value: 84

The corresponding pigment types are thus determined by setting the Zvalue when the Y value of the ink is 55.

(Evaluation of Graininess)

The respective inks used in the examples and comparative examples wereselected as shown below, and printed matter was obtained by printing onPM photographic paper (one example of a medium with a coating layer)using a PM900C ink jet printer (manufactured by Seiko-Epson Co.)according to the Ink Weight Tables 2, 3 and 4 shown in Tables 2 through4 for both a resolution of 720×720 and a resolution of 720×360. Thisrecording matter was visually evaluated according to the criteria shownbelow (graininess (I)).

Similarly, furthermore, recorded matter was obtained by printingISO/JIS-SCID N1A portrait images stipulated by the ISO on PMphotographic paper for both a resolution of 720×720 dots and aresolution of 720×360 dots. The flesh-colored portions of this recordedmatter were judged as shown below by visual inspection (graininess(II)).

(Name of ink combination) Selection from Example 1 → M1, C1 and Y1(Example (1)) Selection from Example 2 → Lm1, Lc1 and Y1 (Example (2)-1)Selection from Example 3 → Lm1, Lc1 and Y2 (Example (3)-1) Lm1, Lc1 andB1 (Example (3)-2) Lm1, Y2 and A1 (Example (3)-3) Selection fromComparative M2, C1 and Y1 (Comparative Example 1 → Example (1))Selection from Comparative Lm2, Lc1 and Y1 (Comparative Example 2 →Example (2)-1) Selection from Comparative Lm2, Lc1 and Y2 (ComparativeExample 3 → Example (3)-1) Lm2, Lc1 and B1 (Comparative Example (3)-2)Lm2, Y2 and A1 (Comparative Example (3)-3)

Ink Weight Table 2 (this table is a matrix in which the respective cellsstipulate the locations where printing was performed.) Magenta ink orlight magenta ink 0.65 0.65 0.60 0.55 0.50 0.40 0.30 0.25 0.15 0.05 0.000.60 0.55 0.55 0.50 0.45 0.35 0.30 0.20 0.15 0.05 0.00 0.50 0.50 0.500.45 0.40 0.30 0.25 0.20 0.10 0.05 0.00 0.45 0.45 0.40 0.40 0.35 0.300.20 0.15 0.10 0.05 0.00 0.40 0.40 0.35 0.35 0.30 0.25 0.20 0.15 0.100.05 0.00 0.35 0.30 0.30 0.30 0.25 0.20 0.15 0.10 0.05 0.05 0.00 0.250.25 0.25 0.20 0.20 0.15 0.15 0.10 0.05 0.05 0.00 0.15 0.15 0.10 0.100.10 0.10 0.05 0.05 0.05 0.00 0.00 Magenta ink or light magenta ink 0.000.05 0.15 0.25 0.30 0.40 0.50 0.55 0.60 0.65 0.65 0.00 0.05 0.15 0.200.30 0.35 0.45 0.50 0.55 0.55 0.60 0.00 0.05 0.10 0.20 0.25 0.30 0.400.45 0.50 0.50 0.50 0.00 0.05 0.10 0.15 0.20 0.30 0.35 0.40 0.40 0.450.45 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.35 0.40 0.40 0.00 0.050.05 0.10 0.15 0.20 0.25 0.30 0.30 0.30 0.35 0.00 0.05 0.05 0.10 0.150.15 0.20 0.20 0.25 0.25 0.25 0.00 0.00 0.05 0.05 0.05 0.10 0.10 0.100.10 0.15 0.15 Yellow ink 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.000.00 0.00 0.05 0.05 0.05 0.10 0.10 0.10 0.10 0.10 0.05 0.05 0.05 0.150.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.20 0.20 0.20 0.250.25 0.25 0.25 0.25 0.20 0.20 0.20 0.25 0.30 0.30 0.30 0.30 0.30 0.300.30 0.30 0.30 0.25 0.35 0.35 0.35 0.40 0.40 0.40 0.40 0.40 0.35 0.350.35 0.40 0.40 0.45 0.50 0.50 0.50 0.50 0.50 0.45 0.40 0.40 0.50 0.550.60 0.65 0.65 0.65 0.65 0.65 0.60 0.55 0.50

Ink Weight Table 3 (this table is a matrix in which the respective cellsstipulate the locations where printing was performed.) Light magenta ink0.65 0.65 0.60 0.55 0.50 0.40 0.30 0.25 0.15 0.05 0.00 0.60 0.55 0.550.50 0.45 0.35 0.30 0.20 0.15 0.05 0.00 0.50 0.50 0.50 0.45 0.40 0.300.25 0.20 0.10 0.05 0.00 0.45 0.45 0.40 0.40 0.35 0.30 0.20 0.15 0.100.05 0.00 0.40 0.40 0.35 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0.350.30 0.30 0.30 0.25 0.20 0.15 0.10 0.05 0.05 0.00 0.25 0.25 0.25 0.200.20 0.15 0.15 0.10 0.05 0.05 0.00 0.15 0.15 0.10 0.10 0.10 0.10 0.050.05 0.05 0.00 0.00 Light cyan ink 0.00 0.05 0.15 0.25 0.30 0.40 0.500.55 0.60 0.65 0.65 0.00 0.05 0.15 0.20 0.30 0.35 0.45 0.50 0.55 0.550.60 0.00 0.05 0.10 0.20 0.25 0.30 0.40 0.45 0.50 0.50 0.50 0.00 0.050.10 0.15 0.20 0.30 0.35 0.40 0.40 0.45 0.45 0.00 0.05 0.10 0.15 0.200.25 0.30 0.35 0.35 0.40 0.40 0.00 0.05 0.05 0.10 0.15 0.20 0.25 0.300.30 0.30 0.35 0.00 0.05 0.05 0.10 0.15 0.15 0.20 0.20 0.25 0.25 0.250.00 0.00 0.05 0.05 0.05 0.10 0.10 0.10 0.10 0.15 0.15 B1 ink 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.05 0.05 0.05 0.10 0.100.10 0.10 0.10 0.05 0.05 0.05 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.150.15 0.15 0.15 0.20 0.20 0.20 0.25 0.25 0.25 0.25 0.25 0.20 0.20 0.200.25 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.25 0.35 0.35 0.350.40 0.40 0.40 0.40 0.40 0.35 0.35 0.35 0.40 0.40 0.45 0.50 0.50 0.500.50 0.50 0.45 0.40 0.40 0.50 0.55 0.60 0.65 0.65 0.65 0.65 0.65 0.600.55 0.50

Ink Weight Table 4 (this table is a matrix in which the respective cellsstipulate the locations where printing was performed.) Light magenta ink0.65 0.65 0.60 0.55 0.50 0.40 0.30 0.25 0.15 0.05 0.00 0.60 0.55 0.550.50 0.45 0.35 0.30 0.20 0.15 0.05 0.00 0.50 0.50 0.50 0.45 0.40 0.300.25 0.20 0.10 0.05 0.00 0.45 0.45 0.40 0.40 0.35 0.30 0.20 0.15 0.100.05 0.00 0.40 0.40 0.35 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0.350.30 0.30 0.30 0.25 0.20 0.15 0.10 0.05 0.05 0.00 0.25 0.25 0.25 0.200.20 0.15 0.15 0.10 0.05 0.05 0.00 0.15 0.15 0.10 0.10 0.10 0.10 0.050.05 0.05 0.00 0.00 A1 ink 0.00 0.05 0.15 0.25 0.30 0.40 0.50 0.55 0.600.65 0.65 0.00 0.05 0.15 0.20 0.30 0.35 0.45 0.50 0.55 0.55 0.60 0.000.05 0.10 0.20 0.25 0.30 0.40 0.45 0.50 0.50 0.50 0.00 0.05 0.10 0.150.20 0.30 0.35 0.40 0.40 0.45 0.45 0.00 0.05 0.10 0.15 0.20 0.25 0.300.35 0.35 0.40 0.40 0.00 0.05 0.05 0.10 0.15 0.20 0.25 0.30 0.30 0.300.35 0.00 0.05 0.05 0.10 0.15 0.15 0.20 0.20 0.25 0.25 0.25 0.00 0.000.05 0.05 0.05 0.10 0.10 0.10 0.10 0.15 0.15 Yellow ink 0.00 0.00 0.000.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.05 0.05 0.05 0.10 0.10 0.100.10 0.10 0.05 0.05 0.05 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.150.15 0.15 0.20 0.20 0.20 0.25 0.25 0.25 0.25 0.25 0.20 0.20 0.20 0.250.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.25 0.35 0.35 0.35 0.400.40 0.40 0.40 0.40 0.35 0.35 0.35 0.40 0.40 0.45 0.50 0.50 0.50 0.500.50 0.45 0.40 0.40 0.50 0.55 0.60 0.65 0.65 0.65 0.65 0.65 0.60 0.550.50(Evaluation Criteria for Graininess (I))

-   A: Recorded matter with a resolution of 720×360 dpi shows no    deterioration in terms of graininess compared to recorded matter    with a resolution of 720×720 dpi.-   B: Recorded matter with a resolution of 720×360 dpi shows some    deterioration in terms of graininess compared to recorded matter    with a resolution of 720×720 dpi.-   C: Recorded matter with a resolution of 720×360 dpi shows    conspicuous deterioration in terms of graininess compared to    recorded matter with a resolution of 720×720 dpi.    (Evaluation Results for Graininess (I))-   (Examples) (1): C, (2)-1: A, (3)-1: A, (3)-2: B, (3)-3: B.-   (Comparative Examples) (1): C, (2)-1: B, (3)-1: B, (3)-2: C, (3)-3:    C.

As is shown in the above evaluation results, in cases where no lightinks were used, the evaluation was B when M1 was used, while theevaluation was C when M2 was used. When neither the ink A nor the ink Bwas used, the deterioration in terms of graininess was less than whenthese inks were used. Furthermore, in cases where Lm1 was used, thedeterioration in terms of graininess was less than in cases where Lm2was used. This appears to be attributable to the fact that the L* value(when the same portions are measured under a D50 light source at avisual field angle of 2 degrees using Gretag Macbeth SPM50 manufacturedby Gretag Co.) in the case of printing at 2.5 mg/inch² on PMphotographic paper (which is one example of a medium with a coatinglayer) is 75 in the case of Lm1, and 70 in the case of Lm2.

(Evaluation Criteria for Graininess (II))

-   A: Recorded matter with a resolution of 720×360 dpi shows no    deterioration in terms of graininess of flesh-colored portions    compared to recorded matter with a resolution of 720×720 dpi.-   B: Recorded matter with a resolution of 720×360 dpi shows some    deterioration in terms of graininess of flesh-colored portions    compared to recorded matter with a resolution of 720×720 dpi.-   C: Recorded matter with a resolution of 720×360 dpi shows    conspicuous deterioration in terms of graininess of flesh-colored    portions compared to recorded matter with a resolution of 720×720    dpi.    (Evaluation Results for Graininess (II))-   (Examples) (1): B, (2)-1: A, (3)-1: A, (3)-2: B, (3)-3: B.-   (Comparative Examples) (1): C, (2)-1: B, (3)-1: B, (3)-2: C, (3)-3:    C.

Thus, in flesh-colored portions, where metamerism and graininess aremost problematical, there was less deterioration in terms of graininessin cases where M1 and Lm1 were used than in cases where M2 and Lm2 wereused.

(Evaluation of Metamerism)

Respective inks used in the examples and comparative examples wereselected as shown below, and recording matter was obtained by printingon PM photographic paper (which is one example of a medium with acoating layer) according to Ink Weight Table 5 shown in Table 5 at aresolution of 720×720 using a PM900C ink jet printer. The Lab valuesstipulated by the CIE were obtained by measuring the same portions undera D50 light source and an A light source at a visual field angle of 2degrees using a Gretag Macbeth SPM50 manufactured by Gretag Co. Next,ΔL*, Δa* and Δb* of the same portions were determined using theequations shown below. ΔE* was determined from these values using theequation shown below, and the results were judged as shown below.ΔL*=L* in the case of the A light source−L* in the case of the D50 lightsourceΔa*=a* in the case of the A light source−a* in the case of the D50 lightsourceΔb*=b* in the case of the A light source−b* in the case of the D50 lightsourceΔE*=(ΔL* ² +Δa* ² +Δb* ²)^(1/2)

(Name of ink combination) Selection from Example 1 → M1, C1 and Y1(Example (1)) Selection from Example 2 → Lm1, Lc1 and Y1 (Example (2)-1)Selection from Example 3 → Lm1, Lc1 and Y2 (Example (3)-1) Selectionfrom Comparative M2, C1 and Y1 (Comparative Example 1 → Example (1))Selection from Comparative Lm2, Lc1 and Y1 (Comparative Example 2 →Example (2)-1) Selection from Comparative Lm2, Lc1 and Y2 (ComparativeExample 3 → Example (3)-4)Ink Weight Table 5 (this table is a matrix in which the respective cellsstipulate the locations where printing was performed.)

Ink Weight Table 5 (this table is a matrix in which the respective cellsstipulate the locations where printing was performed.) Magenta ink orlight magenta ink 13 13 12 11 10 8 6 5 3 1 0 12 11 11 10 9 7 6 4 3 1 010 10 10 9 8 6 5 4 2 1 0 9 9 8 8 7 6 4 3 2 1 0 8 8 7 7 6 5 4 3 2 1 0 7 66 6 5 4 3 2 1 1 0 5 5 5 4 4 3 3 2 1 1 0 3 3 2 2 2 2 1 1 1 0 0 Light cyanink 0 1 3 5 6 8 10 11 12 13 13 0 1 3 4 6 7 9 10 11 11 12 0 1 2 4 5 6 8 910 10 10 0 1 2 3 4 6 7 8 8 9 9 0 1 2 3 4 5 6 7 7 8 8 0 1 1 2 3 4 5 6 6 67 0 1 1 2 3 3 4 4 5 5 5 0 0 1 1 1 2 2 2 2 3 3 Yellow ink 0 0 0 0 0 0 0 00 0 0 1 1 1 2 2 2 2 2 1 1 1 3 3 3 3 3 3 3 3 3 3 3 4 4 4 5 5 5 5 5 4 4 45 6 6 6 6 6 6 6 6 6 5 7 7 7 8 8 8 8 8 7 7 7 8 8 9 10 10 10 10 10 9 8 810 11 12 13 13 13 13 13 12 11 10(Judgement Criteria for Metamerism)

-   -   A: ΔE* is 7.0 or less.    -   B: ΔE* is greater than 7.0 but no greater than 8.0.    -   C: ΔE* is greater than 8.0 but no greater than 10.0.    -   D: ΔE* is greater than 10.0.        (Evaluation Results for Metamerism)

The evaluation results for metamerism according to the abovementionedjudgement criteria are shown in Table 6.

TABLE 6 Metamerism ΔE* Judgement Example (1) 6.9 A Example (2)-1 7.3 BExample (3)-1 8.6 C Comparative Example (1) 7.8 B Comparative Example(2)-1 8.4 C Comparative Example (3)-1 10.3 D

As is shown in the above evaluation results, metamerism showed betterresults when M1 was used than when M2 was used. This is thought to bedue to the fact that the relative intensity difference between the Alight source and the D50 light source at 350 to 500 nm coincide with theintensity distribution of the Z value. Furthermore, metamerism showedbetter results when Lm1 was used than when Lm2 was used. The fact thatΔE* is larger in the case of the light inks than in the case of the darkinks is thought to be attributable to the fact that coloring on PMphotographic paper (which is one type of medium with a coating layer) islow, so the projections in the spectroscopic reflectance spectrum of therecorded matter are severe.

(Evaluation of Color Reproducibility)

The evaluation of color reproducibility was accomplished by judging thesize of the gamut volume and the reproduction of low-lightnesshigh-saturation color images.

(Gamut Volume)

Respective samples of recorded matter were obtained by printing therespective ink sets of the examples and comparative examples on PMphotographic paper (which is one example of a medium with a coatinglayer) at a resolution of 720×720 using a PM900C ink jet printer. Inthis case, the monochromatic duty of 100% was set at 13 mg/inch², andthe mixed color duty was set at 120%, 16 mg/inch². These respective dutyvalues were taken as the maximum duty values, and the reproduciblecolors of the respective ink sets were all printed by varying the dutyvalues 3% at a time within a duty range of 0% to 100% for the respectivemonochromatic inks, and combining all of the respective inks, so thatrespective samples of recorded matter were obtained.

The respective colors of these respective samples of recorded matterwere measured under a D50 light source at a visual field angle of 2degrees using a Gretag Macbeth SPM50 manufactured by Gretag Co., and theLab values stipulated by the CIE were obtained.

The gamut volume (=color reproducibility) was determined from the valuesthus obtained, with the gamut volume in a case where the Lab valuesstipulated by the CIE were all 1 taken as a gamut volume of 1. Ajudgement was performed as shown below on the basis of these values.

(Evaluation Criteria for Gamut Volume)

-   -   A: Gamut volume greater than 730.000.    -   B: Gamut volume greater than 700.000 but no greater than        730.000.    -   C: Gamut volume greater than 680.000 but no greater than        700.000.    -   D: Gamut volume 680.000 or less.        <Evaluation of Low-Lightness High-Saturation Colors>

Furthermore, the respective inks used in the examples and comparativeexamples were selected as shown below, and recorded matter was obtainedby printing on PM photographic paper (which is one example of a mediumwith a coating layer) in accordance with Ink Weight Table 5 shown in theabovementioned Table 5 at a resolution of 720×720 using a PM900C ink jetprinter.

(Name of ink combination) Selection from Example 1 → M1, C1 and Y1(Example (1)) Selection from Example 2 → M1, C1 and Y2 (Example (2)-2)Selection from Example 3 → Lm1, Lc1 and Y2 (Example (3)-1) Selectionfrom Comparative M2, C1 and Y1 (Comparative Example 1 → Example (1))Selection from Comparative M2, C1 and Y1 (Comparative Example 2 →Example (2)-2) Selection from Comparative Lm2, Lc1 and Y2 (ComparativeExample 3 → Example (3)-4)

The recorded matter thus obtained was measured under a D50 light sourceat a visual angle of 2 degrees using a Gretag Macbeth SPM50 manufacturedby Gretag Co., and the Lab values stipulated by the CIE were obtained.C* was determined from these values, and was plotted in a graph with C*on the horizontal axis and L* on the vertical axis. As examples of thegraphs thus obtained, a graph for the dark magenta inks (M1 and M2) isshown in FIG. 1, and the a graph for the light magenta inks (Lm1 andLm2) is shown in FIG. 2. Furthermore, a graph combining both graphs forthe light and dark magenta inks is shown in FIG. 3. A judgement was madeas follows from these graphs.Equation: C*=(a* ² +b* ²)^(1/2)(Evaluation Criteria for Low-Lightness High-Saturation Colors)

-   A: Colors with a saturation of around 95 and a lightness of around    55 can be shown without using black inks.-   B: Colors with a saturation of around 95 and a lightness of around    55 cannot be shown without using black inks.    (Evaluation Results for Color Reproducibility)

The evaluation results for gamut volume and low-lightnesshigh-saturation colors are shown in Table 7.

TABLE 7 Color reproducibility Low-lightness Gamut volume high-saturationExample (1) C A Example (2) C — Example (3) A — Example (2)-2 — AExample (3)-1 — A Comparative Example (1) D B Comparative Example (2) D— Comparative Example (3) B — Comparative Example (2)-2 — B ComparativeExample (3)-1 — B(Comprehensive Evaluation Results)

The abovementioned evaluation results are summarized, and theevaluations for the ink sets of Examples 1 through 3 and ComparativeExamples 1 through 3 are combined with these results, and shown ascomprehensive evaluation results in Table 8. Furthermore, in regard tograininess, the results shown are results obtained by a comprehensiveevaluation from the abovementioned results for graininess (I) and (II).

TABLE 8 Grain- Metam- Gamut Low-lightness iness erism volumehigh-saturation Example 1 B A C A Example (2)-1 A B — — Example (2)-2 —— — A Example (2) A B C A Example (3)-1 A C — A Example (3)-2 B — — —Example (3)-3 B — — — Example (3) A C A A Comparative Example (1) C B DB Comparative Example (2)-1 B C — — Comparative Example (2)-2 — — — BComparative Example (2) B C D B Comparative Example (3)-1 B D — BComparative Example (3)-2 C — — — Comparative Example (3)-3 C — — —Comparative Example (3) B D B B

As is shown in the above evaluation results, the use of M1 or Lm1 makesit possible to reproduce low-lightness high-saturation colors, and thegamut volume is also increased. Thus, the effect of the presentinvention can be obtained by using the ink sets of the respectiveexamples, and controlling the method of use of the respective inks inthese ink sets.

As is clear from the above results, the ink sets of the presentinvention make it possible to obtain superior color reproducibility ofrecorded images even if special color inks other than YMC inks are notused; furthermore it is seen that metamerism can be reduced withoutconspicuous graininess caused by dot expression.

Embodiment B

(Preparation of Inks)

Ink sets comprising the respective inks shown in Table 9 were prepared.The compositions of the inks used in the respective ink sets are shownin Table 10.

Below, furthermore, BYK-348 is a polysiloxane type surfactantmanufactured by BYK-Chemie Japan K.K.

TABLE 9 Ink No. High-concen- Medium-concen- Low-concen- Y M C Lm Lctration Bk tration Bk tration Bk Ink set A (Example 1) 1 2 4 Ink set B(Example 2) 1 2 4 5 7 Ink set C (Example 3) 1 2 4 8 9 10 Ink set D(Example 4) 1 2 4 5 7 8 9 10 Ink set E 1 3 4 (Comparative Example 1) Inkset F 1 3 4 6 7 (Comparative Example 2) Ink set G 1 3 4 8 (ComparativeExample 3) Ink set H 1 3 4 5 7 8 (Comparative Example 4) Ink set I 1 3 45 7 8 9 (Comparative Example 5)

TABLE 10 High-concen- Medium-concen- Low-concen- Y M C Lm Lc tration Bktration Bk tration Bk Ink No. 1 2 3 4 5 6 7 8 9 10 Carbon black 1.500.84 0.22 PV19 6.00 1.00 PR122 6.00 1.00 PY74 6.00 PB15:3 4.00 1.00Dispersing agent 1.50 1.80 1.80 1.20 0.30 0.30 0.30 0.80 0.45 0.12Glycerol 16.00 11.00 17.00 13.00 22.00 17.50 20.00 14.00 19.00 17.001,2-Hexanediol 4.00 4.00 4.00 4.00 5.00 5.00 5.00 8.00 5.00 5.00Ethylene glycol 4.00 7.00 3.00 Triethylene glycol 5.00 HS-500 4.00 5.00BYK348 0.50 0.40 0.40 0.50 0.50 0.50 0.50 0.30 0.50 0.50 EDTA 0.02 0.020.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Triethanol amine 0.90 0.90 0.900.90 0.90 0.90 0.90 0.90 0.90 0.90 Resin emulsion (1) 0.30 0.30 0.300.30 0.30 0.30 1.33 0.30 0.30 Resin emulsion (2) 0.20 0.20 0.20 0.200.20 0.33 2.00 3.00 Resin emulsion (3) 0.30 0.30 0.30 0.30 0.30 2.002.00 Pure water Balance Balance Balance Balance Balance Balance BalanceBalance Balance Balance (Units: wt %)

In each of the above examples, the pigment, dispersing agent and purewater were mixed, and were dispersed for 2 hours together with glassbeads in a sand mill (manufactured by Yasukawa Seisakusho); then, theglass beads (diameter 1.7 mm, 1.5 times amount of mixture (by weight))were removed, thus producing respective pigment dispersions.

Furthermore, the resin emulsion (1) was prepared as follows:

(1) 100 g of dioxane was placed in a glass reaction vessel. 11.8 g ofsulfuric anhydride was added to this while the internal temperature wasmaintained at 25° C., and this mixture was agitated for 2 hours, thusproducing a sulfuric anhydride-dioxane complex.

(2) Next, all of the complex obtained in the abovementioned (1) wasadded to a THF solution (concentration=15%) of 100 g of astyrene/isoprene/styrene tertiary block copolymer (10/80/10 weightratio, Mw=100,000) while the internal temperature was maintained at 25°C., and agitation was continued for an additional 2 hours.

(3) 1200 g of water, 7.1 g of sodium hydroxide and 1 g of sodiumdodecylbenzenesulfonate were placed in a flask, and the internaltemperature was maintained at 40° C. All of the solution obtained in (2)was added to this dropwise for one hour while the internal temperaturewas maintained at 40° C. Following this dropwise addition, the mixturewas agitated for 2 hours at 40° C.; then the solvent was removed (whileleaving the water) by distillation under reduced pressure, thusproducing a sulfonated emulsion C with a concentration of 15%. Thesulfonic acid content in the solid matter was 1.2 mmol/g.

The resin emulsion (2) was a 30% aq solution of a nonionic aqueousemulsion of a modified polypropylene wax, i. e., AQUACER593 (commercialname of product manufactured by BYK-Chemie Japan K.K.).

Furthermore, the resin emulsion (3) was prepared as follows:

55 parts of ethyl acrylate, 37 parts of methyl acrylate, 6 parts ofmethacrylic acid, 3 parts of octyl thioglycolate used as a molecularweight adjusting agent, 2.5 parts of polyvinyl alcohol and 280 parts ofion exchange water were agitated and mixed, thus producing a dispersionof a monomer mixture.

Next, 130 parts of ion exchange water and 2 part of potassium peroxidewere placed in a reaction vessel equipped with an agitator, thetemperature was elevated to 80° C., and the abovementioned monomermixture dispersion was continuously added and polymerized over a periodof 4 hours. Following the completion of this continuous addition, areaction was performed for 30 minutes at 80° C.

Next, an amount of a 10% aqueous solution of sodium hydroxidecorresponding to an amount of sodium hydroxide that was equimolar withthe amount of methacrylic acid used was added to the reaction vessel,and this mixture was heat-treated for 1 hour at 80° C. An appropriateamount of ion exchange water was then added, thus producing a resin witha solid concentration of 15%. The acid value of this resin was 40mgKOH/g, and the pH was 9.2. For the resin in the alkali-solubleemulsion thus obtained, the Mw was 11,000, the glass transitiontemperature (measured according to JIS K6900) was 25° C., the meanparticle size was 50 nm or less, the minimum film formation temperaturewas 15° C., and the turbidity (measured at a cell width of 10 mm using aWATER-ANALYZER 2000 manufactured by Nippon Denko Kogyo K.K.) was 30 g/Lor less.

The solvent (excluding the pigment and dispersing agent) and the resinemulsion prepared as described above were mixed to produce an inksolvent. The respective pigment dispersions prepared as described abovewere respectively added, and the resulting mixtures were agitated for 20minutes at ordinary temperature. The resulting products were filteredwith a 5 μm membrane filter, thus producing respective inks, so that theink sets A through H were obtained.

(1) Evaluation of Graininess

Using the respective ink sets, recorded matter was obtained byperforming image printing at a resolution of 720×720 and a resolution of720×360 on a special ink jet recording paper (PM photographic papermanufactured by Seiko-Epson K.K.) using a PM-4000PX ink jet printer(commercial name of printer manufactured by Seiko-Epson K.K.).Furthermore, since this printer could print only up to 7 colors,printing was performed in two operations in the case of ink sets thatexceeded 7 colors. This recorded matter was judged as follows by visualinspection.

<Judgement Criteria>

-   A Recorded matter with a resolution of 720×360 was not conspicuously    inferior in terms of graininess compared to recorded matter with a    resolution of 720×720.-   B Recorded matter with a resolution of 720×360 was inferior in terms    of graininess compared to recorded matter with a resolution of    720×720.-   C Recorded matter with a resolution of 720×360 was conspicuously    inferior in terms of graininess compared to recorded matter with a    resolution of 720×720.    (2) Evaluation of Metamerism

Using the respective ink sets, recorded matter was obtained byperforming image printing at a resolution of 720×720 on a special inkjet recording paper (PM photographic paper manufactured by Seiko-EpsonK.K.) using a PM-4000PX ink jet printer (commercial name of printermanufactured by Seiko-Epson K.K.). Furthermore, since this printer couldprint only up to 7 colors, printing was performed in two operations inthe case of ink sets that exceeded 7 colors. In the recording matterthus obtained, the same portions were measured under a D50 light sourceand an F11 light source at a visual field angle of 2 degrees using aGretag Macbeth SPM50 manufactured by Gretag Co., and the Lab valuesstipulated by the CIE were obtained. Next, ΔL*, Δa* and Δb; of the sameportions were determined using the equations shown below. ΔE* wasdetermined from these values using the equation shown below, and theresults were judged as shown below.ΔL*=L* in the case of the F11 light source−L* in the case of the D50light sourceΔa*=a* in the case of the F11 light source−a* in the case of the D50light sourceΔb*=b* in the case of the F11 light source−b* in the case of the D50light sourceΔE*=(ΔL* ² +Δa* ² +Δb* ²)^(1/2)

<Evaluation Criteria>

A: ΔE* is 4.0 or less.

B: ΔE* is greater than 4.0 but no greater than 5.0.

C: ΔE* is greater than 5.0 but no greater than 7.0.

D: ΔE* is greater than 7.0.

(3) Evaluation of Color Reproducibility

Using the respective ink sets of the examples and comparative examples,recorded matter was obtained by performing image printing at aresolution of 720×720 on a special ink jet recording paper (MCphotographic paper manufactured by Seiko-Epson K.K.) using a PM4000PXink jet printer (commercial name of printer manufactured by Seiko-EpsonK.K.). Furthermore, since this printer could print only up to 7 colors,printing was performed in two operations in the case of ink sets thatexceeded 7 colors. In this case, the monochromatic duty of 100% was setat 13 mg/inch², and the mixed color duty was set at 120%, 16 mg/inch².These respective duty values were taken as the maximum duty values, andthe reproducible colors of the respective ink sets were all printed byvarying the duty values 3% at a time within a duty range of 0% to 100%for the respective monochromatic inks, and combining all of therespective inks, so that respective samples of recorded matter wereobtained.

The respective colors of these respective samples of recorded matterwere measured under a D50 light source at a visual field angle of 2degrees using a Gretag Macbeth SPM50 manufactured by Gretag Co., and theLab values stipulated by the CIE were obtained.

The gamut volume (=color reproducibility) was determined from the valuesthus obtained, with the gamut volume in a case where the Lab valuesstipulated by the CIE were all 1 taken as a gamut volume of 1. Ajudgement was performed as shown below on the basis of these values.

<Evaluation Criteria>

-   A: Gamut volume greater than 680.000.-   B: Gamut volume 650.000 to 680.000.-   C: Gamut volume less than 650.000.    (4) Stability of Gray Balance (Evaluation of Color Variation)

Using the respective ink sets, recorded matter was obtained byperforming printing at a resolution of 1440×720 on a special ink jetrecording paper (PM photographic paper manufactured by Seiko-Epson K.K.)using a PM-4000PX ink jet printer (commercial name of printermanufactured by Seiko-Epson K.K.). Furthermore, since this printer couldprint only up to 7 colors, printing was performed in two operations inthe case of ink sets that exceeded 7 colors. In the printed patterns,the respective output colors appropriately adjusted so that graycolorless patterns were output with gradation patches divided into 10stages ranging from absolute white (data 0) to absolute black (data255). In the ink sets C and D, since the ink 12 in particular had a lowoutput density (patch 1), this ink was output to an intermediate density(patch 5) up to a maximum 40% duty; furthermore, the ink 11 was outputfrom patch 4 to the high-density patch 10 up to a maximum 40% duty. Thislimitation was not encountered in the ink sets G and H, and appropriateoutput colors were controlled.

Furthermore, in the respective inks, respectively similar gray colorlesspatterns were output in 10-stage patches with the ink weight varied 10%at a time (printing during fluctuation). The colors of the respectivepatches that were output were measured for standard printing andprinting during fluctuation in the Lab color display system of the colordifference display method stipulated by the CIE using a Gretag MacbethSPM50 manufactured by Gretag Co. The color measurement conditions wereas follows: light source D50, no light source filter, whitereference=absolute white, visual field angle 2 degrees.

The color difference ΔE between standard printing and printing duringfluctuation was calculated, and an evaluation was performed using thefollowing criteria:

-   A ΔE 2 or less in all patches.-   B ΔE exceeds 2 in 3 or fewer patches, and is 2 or less in all other    patches.-   C ΔE exceeds 2 in 6 or fewer patches, and is 2 or less in all other    patches.-   D ΔE exceeds 2 in 7 or more patches.

The results of an evaluation performed according to the abovementionedevaluation criteria are shown in Table 11.

TABLE 11 Color Color Ink set Graininess Metamerism reproducibilityvariation Ink set A C A A — Ink set B A A A — Ink set C C A A A Ink setD A A A A Ink set E C C B — Ink set F B C B — Ink set G C C B C Ink setH B C B C Ink set I B C B B

As is shown in Table 11, in the ink sets E and F (comparative examples)using PR-122 as the pigment of the magenta and light magenta inks, theevaluation results for graininess, metamerism and color reproducibilitywere not good. On the other hand, in the ink sets A and B (examples)using PV-19 as the pigment of the magenta and light magenta inks, all ofthe evaluation results were superior. Furthermore, good results thatwere even further improved were obtained in the ink set B that furthercomprised light magenta and light cyan inks.

Furthermore, in the case of the ink sets G, H and I (comparativeexamples) comprising 1 or 2 black inks, color variation was seen. On theother hand, in the case of the ink sets C and D (examples) comprisingthree types of black inks with different pigment concentrations, it isseen that there was little color variation, so that these ink sets weresuperior.

As was described above, the present invention makes it possible toachieve monochromatic or color output with a high quality, to providesuperior color reproducibility of recorded images, to reduce metamerismwithout conspicuous graininess caused by dot expression, and to obtainthe same output at all times without being affected by externalenvironmental factors such as temperature or the like.

The present invention has possibilities for industrial utilization as anink set, recording method, recording apparatus, recording system andrecorded matter that realize superior color reproducibility and areduction in metamerism.

1. An ink set comprising a magenta ink, a yellow ink, and a cyan ink,wherein each of the magenta, yellow and cyan inks comprises pigment inan amount of at least 3 wt % but not more than 10 wt %, wherein themagenta ink (M) comprises C.I. pigment violet 19 and is such that, in acase where the Y value of this ink in the XYZ display system stipulatedby the CIE is 55 as calculated from the ultraviolet-visible transmissionspectrum of a dilute aqueous solution of the ink with a coloringmaterial concentration of 0.01 wt % or less, the Z value of this ink inthe same system is 83 or less, wherein the magenta ink has an L* valuein the CIE-stipulated Lab display system of an aqueous solution of thisink diluted 1000 times by weight of 70 or less, the yellow ink has an L*value in the CIE-stipulated Lab display system of an aqueous solution ofthis ink diluted 1000 times by weight of 95 or less, and the cyan inkhas an L* value in the CIE-stipulated Lab display system of an aqueoussolution of the ink diluted 1000 times by weight of 70 or less, andwherein the ink set further comprises a light magenta ink (Lm)comprising C.I. pigment violet 19 in which the L* value in theCIE-stipulated Lab display system of an aqueous solution of the inkdiluted 1000 times by weight exceeds 70, and a light cyan ink (Lc) inwhich the L* value in the CIE-stipulated Lab system of an aqueoussolution of the ink diluted 1000 times by weight exceeds
 70. 2. The inkset according to claim 1, wherein, the pigment of said yellow ink is C.I. pigment yellow 74, and the pigment of said cyan ink is C. I. pigmentblue 15:3.
 3. The ink set according to claim 1, wherein said lightmagenta ink (Lm) is such that in a case where the Y value in theCIE-stipulated XYZ display system of the ink, as calculated from theultraviolet-visible spectrum of a dilute aqueous solution of the inkwith a coloring material concentration of 0.01 wt % or less, is 55, theZ value of the ink in the same display system is 83 or less.
 4. The inkset according to claim 1, wherein said light magenta ink and said lightcyan ink respectively include pigments at the rate of less than 3 wt %.5. The ink set according to claim 1, which further comprises an ink (A)in which the L* value in the CIE-stipulated Lab display system of anaqueous solution of the ink diluted 1000 times by weight is 50 to 80,the a* value of this aqueous solution is 35 to 85, and the b* value is−5 to 55, and an ink (B) in which the L* value in the CIE-stipulated Labdisplay system of an aqueous solution of the ink diluted 1000 times byweight is 20 to 60, the a* value of this aqueous solution 50 to 90 andthe b* value of this aqueous solution is −90 to −50.
 6. The ink setaccording to claim 1, wherein said inks-contain dispersing agents todisperse said pigments at the rate of 10 to 140 wt % relative to saidpigments.
 7. The ink set according to claim 1, wherein said inks containa high-boiling-point organic solvent at the rate of 0.1 to 30 wt %. 8.The ink set according to claim 1, wherein said inks contain permeationpromoting agents at the rate of 1 to 20 wt %.
 9. The ink set accordingto claim 1, wherein said inks contain acetylene glycol type compoundsand/or silicone type compounds at the rate of 0.1 to 5 wt %.
 10. An inkset comprising a plurality of inks that contain pigments as coloringmaterials, wherein said plurality of inks comprise at least a yellow ink(Y), magenta ink (M) and cyan ink (C), the pigment contained in saidyellow ink is C. I. pigment yellow 74, the pigment contained in saidmagenta ink is C. I. pigment violet 19, and the pigment contained insaid cyan ink is C. I. pigment blue 15:3, and wherein the ink setfurther comprises a light magenta ink (Lm) and a light cyan ink (Lc)that contain the same types of pigments as said magenta ink and cyanink, but have different color densities, wherein the pigment containedin said light magenta ink is C. I. pigment violet 19, and the pigmentcontained in said light cyan ink is C. I. pigment blue 15:3.
 11. The inkset according to claim 10, wherein the pigment content contained in saidyellow ink is 4 to 7 wt %, the pigment content contained in said magentaink is 4 to 7 wt %, and the pigment content contained in said cyan inkis 3 to 6 wt %.
 12. The ink set according to claim 11, wherein thepigment content contained in said light magenta ink is 0.5 to 2 wt %,and the pigment content contained in said light cyan ink is 0.5 to 2 wt%.
 13. An ink set comprising a plurality of inks that contain pigmentsas coloring materials, wherein said plurality of inks comprise at leasta yellow ink (Y), magenta ink (M) and cyan ink (C), the pigmentcontained in said yellow ink is C. I. pigment yellow 74, the pigmentcontained in said magenta ink is C. I. pigment violet 19, and thepigment contained in said cyan ink is C. I. pigment blue 15:3, the inkset further comprising three or more types of black inks with differentpigment concentrations.
 14. The ink set according to claim 13, whereinthe pigment contained in said black inks is carbon black.
 15. The inkset according to claim 13, wherein said three or more types of blackinks with different pigment concentrations are a high-concentrationblack ink with a pigment concentration of 1.5 wt % or greater, amedium-concentration black ink with a pigment concentration of 0.4 wt %or greater but less than 1.5 wt %, and a low-concentration black inkwith a pigment concentration of 0.01 wt % or greater but less than 0.4wt %.
 16. An ink set comprising at least a magenta ink, yellow ink andcyan ink which is used in an ink jet printer, wherein said magenta inkcomprises C.I. pigment violet 19 and has characteristics that thespectroscopic reflectance of this ink is 0.4 or less at least at thewavelength where the spectroscopic reflectance of said yellow ink andthe spectroscopic reflectance of said cyan ink intersect.
 17. The inkset according to claim 16, wherein said magenta ink has characteristicsthat a wavelength region in which the spectroscopic reflectance is 0.4or less is formed at least in the range extending from said intersectionwavelength to a wavelength of 550 nm.
 18. An ink set comprising at leasta magenta ink, yellow ink and cyan ink which is used in an ink jetprinter, wherein said magenta ink comprises C.I. pigment violet 19 andhas characteristics that at the wavelength where the spectroscopicdistributions of said yellow ink and said cyan ink intersect, aspectroscopic reflectance that is 0.4 or less relative to thespectroscopic reflectance values of the yellow ink and cyan ink at thesame wavelength is defined.
 19. The ink set according to claim 18,wherein said magenta ink has characteristics that a spectroscopicreflectance that is 0.4 or less relative to the spectroscopicreflectance of said yellow ink is defined at least in the rangeextending from said intersection wavelength to a wavelength of 550 nm.20. The ink set according to claim 16, wherein said magenta ink containsa styrene-acrylic acid copolymer at the rate of at least 0.7 wt %,glycerol at the rate of at least 15 wt %, ethylene glycol at the rate ofat least 5 wt %, 2-pyrrolidone at the rate of at least 2 wt %,1,2-hexanediol at the rate of at least 5 wt %, and an acetylene glycoltype compound at the rate of at least 0.5 wt %.
 21. The ink setaccording to claim 16, wherein said magenta ink contains one or morehigh-boiling-point compounds selected from among polyhydric alcohol typecompounds and saccharides at the rate of 5% or greater.
 22. The ink setaccording to claim 16, wherein said magenta ink contains one or morepolar solvents selected from among glycol ether type compounds andalkyldiol type compounds at the rate of 1% or greater.
 23. The ink setaccording to claim 16, wherein said magenta ink contains one or moresurfactants selected from among acetylene glycol type compounds,acetylene alcohol type compounds and polysiloxane type compounds at therate of 0.1% or greater.
 24. The ink set according to claim 16, whereinsaid magenta ink contains one or more high-boiling-point compoundsselected from among polyhydric alcohol type compounds and saccharides atthe rate of 5% or greater, one or more polar solvents selected fromamong glycol ether type compounds and alkyldiol type compounds at therate of 1% or greater, and one or more surfactants selected from amongacetylene glycol type compounds, acetylene alcohol type compounds andpolysiloxane type compounds at the rate of 0.1% or greater.
 25. The inkset according to claim 16, wherein said magenta ink contains a resin atthe rate of 0.1% or greater.
 26. The ink set according to claim 20,wherein said yellow ink contains a styrene-acrylic acid copolymer at therate of at least 1 wt %, glycerol at the rate of at least 15 wt %,ethylene glycol at the rate of at least 5 wt %, 2-pyrrolidone at therate of at least 2 wt %, 1,2-hexanediol at the rate of at least 5 wt %,and an acetylene glycol type compound at the rate of at least 0.5 wt %,and said cyan ink contains a styrene-acrylic acid copolymer at the rateof at least 0.5 wt %, glycerol at the rate of at least 15 wt %, ethyleneglycol at the rate of at least 5 wt %, 2-pyrrolidone at the rate of atleast 2 wt %, 1,2-hexanediol at the rate of at least 5 wt %, and anacetylene glycol type compound at the rate of at least 0.5 wt %.
 27. Theink set according to claim 16, wherein the coloring material of saidcyan ink is constituted by “C. I. pigment blue 15:3”, and the coloringmaterial of said yellow ink is constituted by “C. I. pigment yellow 74”,and the coloring material of said magenta ink is constituted by “C. I.pigment violet 19”.
 28. A recording method comprising forming imagesusing the ink set described in claim
 1. 29. An ink jet recording methodcomprising forming mixed color portions with the magenta ink, yellow inkand cyan ink in the ink set according to claim
 1. 30. A recordingapparatus comprising means for realizing the recording method accordingto claim
 28. 31. An ink jet recording apparatus comprising the ink setaccording to claim
 1. 32. A recording system for forming imagescomprising the ink set according to claim
 1. 33. Recorded matter inwhich images are formed by deposition of the ink set according to claim1 onto a recording medium.